import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Iterator;


public class Main_yukicoder320 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Printer pr = new Printer(System.out);

        int n = sc.nextInt();
        long m = sc.nextLong();

        long[] a = new long[n + 1];
        a[1] = 1;
        a[2] = 1;
        for (int i = 3; i <= n; i++) {
        	a[i] = a[i - 1] + a[i - 2];
        }

        long[] diff = new long[n + 1];
        for (int j = 3; j <= n; j++) {
        	long[] b = new long[n + 1];
        	b[1] = 1;
        	b[2] = 1;
        	for (int i = 3; i <= n; i++) {
        		b[i] = b[i - 1] + b[i - 2];
        		if (i == j) {
        			b[i]--;
        		}
        	}

        	diff[j] = a[n] - b[n];
        }

        long d = a[n] - m;
        int cnt = 0;
        for (int i = 3; i <= n; i++) {
        	if (d - diff[i] >= 0) {
        		d -= diff[i];
        		cnt++;
        	}
        }

        if (d != 0) {
        	pr.println(-1);
        } else {
        	pr.println(cnt);
        }

        pr.close();
        sc.close();
    }

	@SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;
		Iterator<String> it;

		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}

		String next() throws RuntimeException  {
			try {
				if (it == null || !it.hasNext()) {
					it = Arrays.asList(br.readLine().split(" ")).iterator();
				}
				return it.next();
			} catch (IOException e) {
				throw new IllegalStateException();
			}
		}

		int nextInt() throws RuntimeException {
			return Integer.parseInt(next());
		}

		long nextLong() throws RuntimeException {
			return Long.parseLong(next());
		}

		float nextFloat() throws RuntimeException {
			return Float.parseFloat(next());
		}

		double nextDouble() throws RuntimeException {
			return Double.parseDouble(next());
		}

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new IllegalStateException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}