想不通，真的想不出来是哪里出了问题了 求大佬帮忙检查一下：

#include<stdio.h>

long long a[1110][1110]={0};
long long b[1110][1110]={0};

int main(void){
    int n,m,c;
    scanf("%d %d %d",&n,&m,&c);

    int i,j;
    for(i=1 ; i<=n ; i++){
        for(j=1 ; j<=m ; j++){
            scanf("%lld",&b[i][j]);
            a[i][j] = a[i-1][j] + a[i][j-1] - a[i-1][j-1] +b[i][j];
        }
    }
    long long temp;
    long long best=-922337203685477580;
    int x,y;
    for(i=1 ; i+c<=n ; i++){
        for(j=1 ; j+c-1<=n ; j++){
            temp = a[i+c-1][j+c-1] - a[i-1][j+c-1] - a[i+c-1][j-1] + a[i-1][j-1];
            if(temp > best){
                best = temp;
                x=i,y=j;
            }
        }
    }
    printf("%d %d",x,y);
    return 0;
}