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


int main() {
    long long n,m;
    cin>>n>>m;
    if(n==1)
        cout<<m-1;
    else if(m==1)
        cout<<n-1;
    else if(n==1 && m==1)
        cout<<0;
    else
        cout<<m*n-1;
        /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}