算法1

猜了个结论过了~~

C++ 代码

#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int mod=1e9+7;
const int N=1e5+10;

int main()
{
    int n,m;
    cin>>n>>m;
    cout<<n*m-n-m<<endl;
    return 0;
}

```