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


int recur(int n, int m){
    if(n == 1 && m == 1) return 0;
    if(n != 1) return (n-1) * recur(1, m);
    /*    int mid = n / 2;
        return 1 + recur(mid, m) + recur(n-mid, m);
    }*/
    int mid = m / 2;
    return 1 + recur(n, mid) + recur(n, m-mid);
}

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