#ifdef LOCAL
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
#define ll long long
#define rep(i,n) for(ll i=0;i<(ll)n;i++)
#define all(v) v.begin(),v.end()
const ll INF = (ll)2e18;

/*
素数判定(エラトステネス)
    下処理O(NloglogN)
    実行O(1)
    pをtureにしp*p以上のpの倍数をfalseに
N以下の自然数がprimeかを表す配列を返す関数
*/
vector<bool> make_is_prime(int N) {
    vector<bool> prime(N + 1, true);
    prime[0] = false;
    prime[1] = false;
    for (int i = 2; i * i <= N; i++) {
        if (!prime[i]) continue;
        for (int j = i * i; j <= N; j += i) {
            prime[j] = false;
        }
    }
    return prime;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    ll N;
    cin >> N;
    ll ans = sqrt(N);
    while(ans*ans>N){
        ans--;
    }
    while(ans*ans<=N&&(ans+1)*(ans+1)<=N){
        ans++;
    }
    cout << ans << endl;
}