#include<bits/stdc++.h>
using namespace std;
const int N = 1e6+0;
#define int long long
#define Yes cout<<"Yes"<<endl
#define No  cout<<"No"<<endl
#define f first
#define s second
const int M = 1e9+7;
#define all(x) (x).begin(),(x).end()
#define setprecision(x) fixed<<setprecision((int)(x))
bool odd(int num) {return ((num & 1) == 1);}
bool even(int num) {return ((num & 1) == 0);}
const int inf = 1e18;
   

void solve(){
    int n;
   cin>>n;
   int cnt = sqrt(n);
   for(int i=1;i<cnt;i++){
    if(i*(i+1)<=n){
        cnt++;
    }
   }
   cout<<cnt<<endl;
}

int32_t main(){ 
    ios::sync_with_stdio(0);cin.tie(0);
 
    solve();
    
   
    
 
    // int t;
    // cin>>t;
    // for(int T=1;T<=t;T++){
    //    //cout<<"Case "<<T<<": "; 
    //    solve();
    // }
 
    return 0;
}