#include <iostream>

using namespace std;

int main() {
    long long int n, m;
    cin >> n >> m;

    if(n>m) {
        long long int tmp = n;
        n = m;
        m = tmp;
    }

    long long int rez = n*n*m - n*(n-1)*(n+3*m+1)/6;
    cout << rez << endl;
}