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

unordered_map<long long, long long> mp;

long long solve(long n, long m)
{
    if (mp[n*m]) return mp[n*m];
    long long count = 0ll, tmp;
    for (int i = 1; i <= n - 1; ++i)
        if ((tmp = 1 + solve(n - i, m) + solve(i, m)) > count) count = tmp;
    for (int i = 1; i <= m - 1; ++i)
        if ((tmp = 1 + solve(n, m - i) + solve(n, i)) > count) count = tmp;
    return mp[n*m] = count;
}

int main() {
    long n, m;
    cin >> n >> m;
    cout << solve(n, m);
    return 0;
}