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


int main() {
    long long int i,j,n,m;
    cin>>n>>m;
    
    if(n==1 && m==1)
        {
        cout<<"0\n";
        return 0;
    }
    
    if(n==1)
        cout<<m-1<<endl;
    else
        {
        if(m==1)
            cout<<n-1<<endl;
        else
            cout<<m-1+m*(n-1)<<endl;
    }
    return 0;
}