#include <iostream>
#include <cmath>
using namespace std;

int main(){
    int n; cin >> n;
    int count;
    if(n == 1) cout << "0" << endl;
    else if(n%2 == 1) cout << (n + 1)/2 -1 << endl;
    else if(n == 2) cout << "1" << endl;
    else if(n == 4) cout << "2" << endl;
    else {
        for(int i = 3; i < n; i++){
            count = i;
            if(pow(2,i) >= n){
                cout << count -1 << endl;
                break;
            }
        }
    }
    return 0;
}