#include "bits/stdc++.h"
using namespace std;
#ifdef _DEBUG
#include "dump.hpp"
#else
#define dump(...)
#endif

#define int long long
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define all(c) begin(c),end(c)
const int INF = sizeof(int) == sizeof(long long) ? 0x3f3f3f3f3f3f3f3fLL : 0x3f3f3f3f;
const int MOD = 1'000'000'007;
template<class T> bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, const T &b) { if (b < a) { a = b; return true; } return false; }

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N, M; cin >> N >> M;
	vector<int> a(N);
	a[0] = a[1] = 1;
	rep(i, 0, N - 2) {
		a[i + 2] = a[i + 1] + a[i];
	}
	int d = a[N - 1] - M;
	int cnt = 0;
	rrep(i, 0, N - 2) {
		dump(d);
		if (d >= a[i]) {
			d -= a[i];
			cnt++;
		}
	}
	if (d == 0) {
		cout << cnt << endl;
	}
	else {
		cout << -1 << endl;
	}
	return 0;
}