#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef complex<double> P;
typedef pair<int,int> pii;
#define REP(i,n) for(ll i=0;i<n;++i)
#define REPR(i,n) for(ll i=1;i<n;++i)
#define FOR(i,a,b) for(ll i=a;i<b;++i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define MOD (ll)(1e9+7)
#define ADD(a,b) a=((a)+(b))%MOD
#define FIX(a) ((a)%MOD+MOD)%MOD

int main(){
  ll n,m;
  cin >> n >> m;
  vl fib(n);
  fib[0] = 1;
  fib[1] = 1;
  FOR(i,2,n)fib[i] = fib[i-1]+fib[i-2];
  if(fib[n-1] < m){
    cout << -1 << endl;
    return 0;
  }
  ll sa = fib[n-1] - m;
  ll result = 0;
  REP(_i,n-2){
    ll i = n-3-_i;
    if(fib[i]<=sa){
      sa -= fib[i];
      ++result;
    }
  }
  if(sa!=0)result = -1;
  cout << result << endl;
  return 0;
}