题解

#include<iostream>
using namespace std;
int main()
{
	int a,num=0,c=0;
	cin>>a;
	for(int i=1;i<=a;0)
	{
		num++;
		for(int j=1;j<=num and i<=a;j++)
		{
			c+=num;
			i++;
		}
	}
	cout<<c;
}