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

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll n;
    cin >> n;
    ll ans = sqrtl(n) - 5;
    while((ans + 1) * (ans + 1) <= n) ans++;
    cout << ans << '\n';
}