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


int main() {
    long long int n,m;
    scanf("%lld%lld",&n,&m);
    if (n<m) swap(n,m);
    printf("%lld\n",max((long long)0,(n-1)*m+m-1));
    return 0;
}