#include<cstdio>
#include<iostream>
using namespace std;
int main()
{
    int c,b,a=0;
    cin>>c;
    for(b=1;c-b>=0;c-=b++)
    {
    	c+=b*b;
	} 
	cout<<c+a*b<<endl;
    		
	
		return 0;
}