B3749 [语言月赛202304] Matrix

请问这道题是什么意思？本蒟蒻没有看懂。

好像要hack一个代码什么的:

#include <bits/stdc++.h>
using namespace std;

int a[2005][2005], b[2005][2005];
int f[2005][2005], n;

int main() {
    scanf("%d", &n);
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= n; ++j)
            scanf("%d", &a[i][j]);
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= n; ++j)
            scanf("%d", &b[i][j]);
    for (int i = 0; i <= n; ++i)
        for (int j = 0; j <= n; ++j)
            f[i][j] = 1000000000;
    f[1][1] = 0;
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= n; ++j) {
            if (i == 1 && j == 1)
				continue;
			f[i][j] = min(f[i][j], f[i - 1][j] + b[i - 1][j]);
			f[i][j] = min(f[i][j], f[i][j - 1] + a[i][j - 1]);
        }
    int ans = 1000000000;
    ans = min(ans, f[n - 2][n]);
    ans = min(ans, f[n][n - 2]);
    ans = min(ans, f[n - 1][n - 1]);
    printf("%d\n", ans);
    return 0;
}

请大佬帮忙解释一下。