PatratMagic4

#include <iostream>
using namespace std;

int main()
{
    long int c,n=0;
    cin>>c;
    do
        ++n;
    while(((n*n+1)*n)/2!=c&&n<c);
    if((n*n+1)*n/2==c)
        cout<<n;
    else
        cout<<0;
    return 0;
}