2点WA了

#include<bits/stdc++.h>
using namespace std;
int m,n,s,a;
int main(){
	//freopen("b.in","r",stdin);
	//freopen("b.out","w",stdout);
	cin>>m>>n;
	if(n==1&&m==1){
		cin>>a;
		cout<<a;
		return 0;
	}
	int a[m+2][n+2];
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			cin>>a[i][j];
			if(i==1){
				s+=a[i][j];
			}
			else if(i==n){
				s+=a[i][j];
			}
			else if(j==1){
				s+=a[i][j];
			}
			else if(j==m){
				s+=a[i][j];
			}
		}
	}
	cout<<s;
	//fclose(stdin);fclose(stdout);
	return 0;
}