typedef unsigned long long ll;
/*ll sum = ((n + 1) * n / 2) * ((m + 1) * m / 2);*/
	ll sum1 = (n + 1) * n / 2, sum2 = (m + 1) * m / 2;
	ll sum = sum1 * sum2;

$n\leq5000,m\leq5000$

$5001\ast5000\div2\ast5001\ast5000\div2$

直接算也不会爆啊，，，为什么直接硬算的答案不对。。。。。