题解

#include<bits/stdc++.h>
using namespace std;
int main(){
    int n ,m ,sum = 0 ,x;
    cin >> n >> m;
    for (int i = 1 ; i <= n ; i++){
        for (int j = 1 ; j <= m ; j++){
            cin >> x;
            if (i == 1 || i == n || j == 1 || j == m)  //如果位于边缘
                sum += x;
        }
    }
    cout << sum;
    return 0;
}