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

#define Alhamdulillah ios_base::sync_with_stdio(0), cin.tie(0);
#define ll long long
#define ull unsigned long long
#define endl '\n'
#define db(i) cout << "c -> " << i << endl;
#define pv(v) for(auto e : v)   cout << e << " ";   cout << endl;
#define pm(m) for(auto [x,y] : m)   cout << x << " " << y << endl;   cout << endl;

void solve(){
    int n;  cin >> n;
    int a = 1, b = 1, ct = 0;
    while(a*b <= n){
        ct++;
        if(a == b)  b++;
        else    a++;
    }
    cout << ct;
}

int main(){
    Alhamdulillah
    int t=1;    //cin >> t;
    while(t--)  solve();
    return 0;
}