#include <iostream>
#include <cmath>
using namespace std;
int k=0;int x;
int f(int n)
{

    k+=pow(n,2);
    if(k>=x)
    {
        return n;
    }
    n++;
    return f(n);
}
int main()
{


   cin>>x;
   cout<<f(0)-1;
    return 0;
}