#include<bits/stdc++.h>
using namespace std;

#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

using ll=long long;

int main(){
	ll N;cin>>N;
	using i128=__int128_t;

	i128 l=0,r=N+1;
	while(r-l>1){
		i128 mid=(l+r)>>1;
		if(mid*mid<=N)l=mid;
		else r=mid;
	}
	cout<<ll(l)<<endl;
}