#include <bits/stdc++.h>
using namespace std;

int main() {
  long long n, k;
  cin >> n >> k;
  cout << (2 * k * k * k - 3 * k * k * n - 6 * k * k + 3 * k * n - 2 * k + 
           n * n * n + 3 * n * n + 8 * n + 12) / 6 % 1000000007 << endl;
  return 0;
}