C language array direction

#include <stdio.h>
#define maxn 20
//ep11

int grid[maxn + 5][maxn + 5];
int dir[4][2] = {
    {-1, -1}, {-1, 0}, {-1, 1} ,{0, 1}
};

int calc(int x, int y) {
    int ans = 0;
    for(int k = 0; k < 4; k++) {
        int p = 1;
        for(int step = 0; step < 4; step++) {
            int dx = x + dir[k][0] * step;
            int dy = y + dir[k][1] * step;
            if(dx < 0 || dx >= maxn) break;
            if(dy < 0 || dy >= maxn) break;
            p *= grid[dx][dy];
        }
        if(p > ans) ans = p;
    }
    return ans;
}

int main() {
    int ans = 0;
    for (int i = 0; i < maxn; i++)
    {
        for(int j = 0; j < maxn; j++) {
            scanf("%d",&grid[i][j]);
        }
    }

        for (int i = 0; i < maxn; i++)
        {

            for (int j = 0; j < maxn; j++)
            {

                int p = calc(i, j);
                if(p > ans) {
                    ans = p;
                }
                /* code */
            }
            
            /* code */
        
        
        /* code */
        }
    printf("%d\n", ans);
    
    return 0;
}