#include<stdio.h>
int main() {
    int sum=0,m,n,M,N,a[101][101];
    scanf("%d %d", &m, &n);//行

    for (M = 1; M <= m; M++)      
        for (N = 1; N <= n; N++)
            scanf("%d", &a[M][N]);//输入二维数组
            if (M == 1 || N == 1 || M == m || N == n) {
                sum = sum + a[M][N];
            }

 printf("%d", sum);

    return 0;

}

不知道哪里出问题了输出是0