#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <functional>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <map>
#include <set>
#include <bitset>
#include <cassert>
#include <exception>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll,ll> P;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<string> vs;
typedef vector<P> vp;
#define rep(i,a,n) for(ll i = (a);i < (n);i++)
#define per(i,a,n) for(ll i = (a);i > (n);i--)
#define lep(i,a,n) for(ll i = (a);i <= (n);i++)
#define pel(i,a,n) for(ll i = (a);i >= (n);i--)
#define clr(a,b) memset((a),(b),sizeof(a))
#define pb push_back
#define mp make_pair
#define all(c) (c).begin(),(c).end()
#define sz size()
#define print(X) cout << (X) << endl
const ll INF = 1e+9+7;
ll n,m,l;
string s,t;
ll d[200010],dp[550][550];

int main(){
  cin >> n;
  m = 0;
  l = 0;
  while(n > 0){
    if(n % 2)m++;
    n /= 2;
    l++;
  }
  //cout << m << " " << l << endl;
  print(max(m,l-1));
  return 0;
}
