#include <stdio.h>
#include <algorithm>
#include <vector>
#include <deque>
#include <string>
#include <iostream>
using namespace std;
using ll = long long;

void solve();
int main() {
	solve();
#ifdef DBG
	while (true);
#endif
}

//508
void solve() {
	ll n, i;
	scanf("%lld", &n);

	for (i = 1; i < n; i++) {
		if (abs(i * i * 3 - n) > 1000000)
			continue;
		printf("%lld\n", i);
		break;
	}
}