#include <iostream>
#include <cmath>
using namespace std;
int main() 
{
	long long x;
	cin >> x;
	long long n = 1;
	long long sum = 0;
	while (sum + n * n <= x) 
    {
		sum += n * n;
		n++;
	}
	cout << n - 1 << endl;
	return 0;
}

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