#define _CRT_SECURE_NO_WARNINGS
#include<sstream>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<climits>
#include<cmath>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<numeric>
#include<functional>
#include<algorithm>
#include<bitset>
#include<tuple>
#include<unordered_set>
#include<random>
using namespace std;
#define INF (1<<29)
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define all(v) v.begin(),v.end()
#define uniq(v) v.erase(unique(all(v)),v.end())
#define indexOf(v,x) (find(all(v),x)-v.begin())





int main() {
	long long n, m;
	long long a, b, c;
	cin >> n >> m;
	a = b = 1;
	int ans = 0;
	vector<long long> fib;
	fib.push_back(1);
	rep (i,n-2) {
		if (i + 3<n)fib.push_back(b);
		c = a + b;
		a = b;
		b = c;
	}
	for (int i = fib.size() - 1; i >= 0;i--) {
		if (c-m>=fib[i]) {
			c -= fib[i];
			ans++;
		}
	}
	if (c != m)ans = -1;
	cout << ans << endl;


	return 0;
}