diff --git a/Day17/Day17A.c b/Day17/Day17A.c
new file mode 100644
index 0000000..28182ab
--- /dev/null
+++ b/Day17/Day17A.c
@@ -0,0 +1,197 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <assert.h>
+#include <string.h>
+
+#define AT(x, y) grid[(y) * x_max + (x)]
+
+void get_limits(FILE *file, int *x_min, int *x_max, int *y_min, int *y_max) {
+    char *line = NULL;
+    size_t len;
+
+    *x_min = INT_MAX;
+    *x_max = INT_MAX;
+    *x_max = 0;
+    *y_max = 0;
+
+    while (getline(&line, &len, file) != -1) {
+        int xa, xb, ya, yb;
+        if (sscanf(line, "x=%d, y=%d..%d", &xa, &ya, &yb) == 3) {
+            if (xa < *x_min) *x_min = xa;
+            if (xa + 1 > *x_max) *x_max = xa + 1;
+            if (ya < *y_min) *y_min = ya;
+            if (yb + 1 > *y_max) *y_max = yb + 1;
+        } else if (sscanf(line, "y=%d, x=%d..%d", &ya, &xa, &xb) == 3) {
+            if (xa < *x_min) *x_min = xa;
+            if (xb + 1 > *x_max) *x_max = xa + 1;
+            if (ya < *y_min) *y_min = ya;
+            if (ya + 1 > *y_max) *y_max = yb + 1;
+        } else {
+            break;
+        }
+    }
+
+    *x_max += 10;
+        *x_min -= 10;
+    printf("grid: x=%d..%d y=%d..%d\n", *x_min, *x_max, *y_min, *y_max);
+
+    rewind(file);
+}
+
+void build_grid(FILE *file, char *grid, int x_max) {
+    char *line = NULL;
+    size_t len;
+    while (getline(&line, &len, file) != -1) {
+        int xa, xb, ya, yb;
+        if (sscanf(line, "x=%d, y=%d..%d", &xa, &ya, &yb) == 3) {
+            printf("x=%d, y=%d..%d\n", xa, ya, yb);
+            for (int y = ya; y <= yb; y++)
+                AT(xa, y) = '#';
+        } else if (sscanf(line, "y=%d, x=%d..%d", &ya, &xa, &xb) == 3) {
+            printf("x=%d..%d, y=%d\n", xa, xb, ya);
+            for (int x = xa; x <= xb; x++)
+                AT(x, ya) = '#';
+        } else {
+            break;
+        }
+    }
+    grid[500] = '+';
+}
+
+void print_grid(char *grid, int x_min, int x_max, int y_min, int y_max) {
+    printf("\n");
+    printf("      "); for (int x = x_min; x < x_max; x++) printf("%d", x / 100 % 10);  printf("\n");
+    printf("      "); for (int x = x_min; x < x_max; x++) printf("%d", x / 10 % 10);   printf("\n");
+    printf("      "); for (int x = x_min; x < x_max; x++) printf("%d", x % 10);        printf("\n");
+
+    for (int y = 0; y < y_max + 3; y++) {
+        if (y < y_min || y >= y_max)
+            printf("\033[41m");
+        printf("%4d  \033[0m", y);
+        for (int x = x_min; x < x_max; x++) {
+            switch (grid[y * x_max + x]) {
+            case '.':
+                putchar(' ');
+                putchar(' ');
+                break;
+
+            case '|':
+                printf("\033[44m\u2551\u2551\033[0m");
+                break;
+
+            case '~':
+                printf("\033[44m\u2248\u2248\033[0m");
+                break;
+
+            case '#':
+                printf("\033[33m\u2588\u2588\033[0m");
+                break;
+
+            case '+':
+                printf("\033[41m\u256C\u256C\033[0m");
+                break;
+
+            default:
+                assert(0);
+            }
+        }
+        putchar('\n');
+    }
+}
+
+char *read_grid(FILE *file, int *x_min, int *x_max, int *y_min, int *y_max) {
+    get_limits(file, x_min, x_max, y_min, y_max);
+
+    size_t size = (*y_max + 50) * *x_max;
+    char *grid = malloc(size);
+    memset(grid, '.', size);
+
+    build_grid(file, grid, *x_max);
+    return grid;
+}
+
+
+void step(char *grid, int x_min, int x_max, int y_min, int y_max) {
+    for (int y = 0; y < y_max + 50; y++) {
+        for (int x = x_min; x < x_max; x++) {
+            if (AT(x, y) == '+' || AT(x, y) == '|') {
+                if (AT(x, y + 1) == '.') {
+                    AT(x, y + 1) = '|';
+                } else if (AT(x, y + 1) == '#' || AT(x, y + 1) == '~') {
+                    int is_still = 1;
+                    int left_wall = -1, right_wall = -1;
+
+                    for (int x_ = x; x_ >= x_min - 1; x_--) {
+                        if (AT(x_, y) == '#') {
+                            left_wall = x_ + 1;
+                            break;
+                        } else if (AT(x_, y + 1) == '.' || AT(x_, y + 1) == '|') {
+                            is_still = 0;
+                            left_wall = x_;
+                            break;
+                        }
+                    }
+
+                    for (int x_ = x; x_ <= x_max; x_++) {
+                        if (AT(x_, y) == '#') {
+                            right_wall = x_ - 1;
+                            break;
+                        } else if (AT(x_, y + 1) == '.' || AT(x_, y + 1) == '|') {
+                            is_still = 0;
+                            right_wall = x_;
+                            break;
+                        }
+                    }
+
+                    if (left_wall != -1 && right_wall != -1) {
+                        for (int x_ = left_wall; x_ <= right_wall; x_++) {
+                            assert(AT(x_, y) != '#');
+                            AT(x_, y) = is_still ? '~' : '|';
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+int count_water(char *grid, int x_min, int x_max, int y_min, int y_max) {
+    int water = 0;
+    for (int y = y_min; y < y_max; y++) {
+        for (int x = x_min; x < x_max; x++) {
+            water += (AT(x, y) == '~') ? 1 : 0;
+        }
+    }
+    return water;
+}
+
+int main(int argc, char **argv) {
+    if (argc != 2) {
+        printf("Usage: %s [input]\n", argv[0]);
+        return EXIT_FAILURE;
+    }
+    FILE *file = fopen(argv[1], "r");
+
+    int x_min, x_max, y_min, y_max;
+    char *grid = read_grid(file, &x_min, &x_max, &y_min, &y_max);
+
+    print_grid(grid, x_min, x_max, y_min, y_max);
+    int last_water = -1, water = -1;
+    int extra_steps = 0;
+    do {
+        step(grid, x_min, x_max, y_min, y_max);
+
+        last_water = water;
+        water = count_water(grid, x_min, x_max, y_min, y_max);
+        printf("Water: %d\r", water);
+
+        if (last_water == water)
+            extra_steps += 1;
+        else
+            extra_steps = 0;
+    } while (extra_steps < 200);
+
+    print_grid(grid, x_min, x_max, y_min, y_max);
+    printf("Water: %d\n", water);
+}