#include <bits/stdc++.h>
#define  Rep(i,j,n) for(li i=(j);i<(n);i++)
#define  rep(i,n) Rep(i,0,(n))
#define  all(a) begin(a),end(a)
using namespace std;
typedef long int li;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<string> vs;

int main()
{
    int n,ans=0;
    cin>>n;
    for(int i=1;i<n;i*=2) ans++;
    cout<<ans<<endl;
    return 0;
}