#include<iostream>
#include<vector>
using namespace std;

int main()
{
	long long N;
	cin >> N;
	long long ok = -1;
	long long ng = 1e9+20;
	while(abs(ng-ok) > 1LL)
	{
		long long mid = (ok + ng) / 2;
		if(mid * mid <= N) ok = mid;
		else ng = mid;
	}
	cout << ok << endl;
}