题解

#include<iostream>
using namespace std;
int main(){
    long long n,a[1010][1010],sum=0;
    cin>>n;
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            cin>>a[i][j];
            if(j==0&&i==0||i==n-1&&j==0||i==0&&j==n-1||i==n-1&&j==n-1){
                continue;
            }
            sum+=a[i][j];
        }
    }
    cout<<sum;
    return 0;
}