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

int main(){
    ll n, m, res = 0;
    cin >> n >> m;
    
    vector<ll> a(n);
    a[0] = a[1] = 1;
    for(int i = 2; i < n; i++) a[i] = a[i - 1] + a[i - 2];
    m = a[n - 1] - m;

    for(int i = n - 3; i >= 0; i--){
        if(m >= a[i]){
            m -= a[i];
            res++;
        }
    }
    
    cout << (m ? -1 : res) << '\n';
}