#include <iostream>

using namespace std;

int main() {
    long long int n, m;
    cin >> n >> m;
    if(n < 1 || n > 1000000 || m < 1 || m > 1000000) {
        cout << "-1" << endl;
        return -1;
    }

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

    // long long int rez = n*n*m - (n+m)*((n*(n-1))/2) + ((n*(n-1)*(2*n-1))/6);
    long long int rez = n*n*m - (n*(n-1)*(n+3*m+1)/6);
    cout << rez << endl;
}