#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;

long long n,m, maxi, mini, cnt;
int main() {
    long long n,m;
    cin>>n>>m;
    if(n==1 && m==1)
        {
        cout<<0;
    }else
        {
        cout<<(n*m)-1;
    }
}