#include<iostream>
using namespace std;
int main()
{
	int day, coin = 1,sum = 0;
	cin >> day;
	for (int i = 0;i < day;i++)
	{
		for (int k = 0; k < coin; k++)
		{
			sum += coin;
		}
		coin++;
		if (coin == day)
		{
			break;
		}
	}
	cout << sum << endl;
	system("pause");
	return 0;
}

我的想法是两个循环，内循环进行累加，外循环进行金币的递增，为啥这样结果有点问题呢？