#include <iostream>
#include <stdio.h>
#include <math.h>
using namespace std;
typedef long long LL;
int main(int argc, char* argv[])
{
	LL N;
	cin>>N;
	LL r2=N/3;
	LL r=(LL)sqrt((double)r2)+1000000;
	printf("%lld\n",r);
	
	return 0;
}