Codeforces 821B

原点，（x,y）形成的矩形内的坐标之和为x*(x+1)/2*(y+1)+y*(y+1)/2*(x+1);

#include<iostream>
#include<algorithm>
#include<string>
#include<string.h>
#include<cmath>
using namespace std;
typedef long long ll;
int main()
{
    int n, m, b;
    while (cin >> m >> b)
    {
      ll  maxx = 0;
        for (int y = 0; y <=b; y++)
        {
            ll x = (b - y) * m;
            ll cur = x*(1 + x) / 2 * (1 + y) + y*(y + 1) / 2 * (x + 1);
            maxx = max(cur, maxx);
        }
        cout << maxx << endl;
    }
    return 0;
}