include <bits/stdc++.h>

using namespace std;
int n, b,c,d,S;
float a;
int main()
{
cin >> n;
a = (sqrt(1+8n)-1)/2;
if ( a == int(a))
a = a;
else
a = a+1;
b = (aa+a)/2;
c = b - n;
d = (a(a+1)(2a+1))/6;
S = d - ca;

cout << S;

return 0;

}