use std::io::Read;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let mut n: u64 = itr.next().unwrap().parse().unwrap();
    let mut m: u64 = itr.next().unwrap().parse().unwrap();

    let mut i = 2;
    let mut nprime = std::collections::HashMap::new();
    let mut mprime = std::collections::HashMap::new();
    while i * i <= n {
        while n % i == 0 {
            let num = nprime.entry(i as usize).or_insert(0);
            mprime.entry(i as usize).or_insert(0);
            *num += 1;
            n /= i;
        }
        i += 1;
    }
    if n != 1 {
        let num = nprime.entry(n as usize).or_insert(0);
        mprime.entry(n as usize).or_insert(0);
        *num += 1;
    }

    i = 2;
    while i * i <= m {
        while m % i == 0 {
            nprime.entry(i as usize).or_insert(0);
            let num = mprime.entry(i as usize).or_insert(0);
            *num += 1;
            m /= i;
        }
        i += 1;
    }
    if m != 1 {
        nprime.entry(m as usize).or_insert(0);
        let num = mprime.entry(m as usize).or_insert(0);
        *num += 1;
    }

    let mut ans: u64 = 1;
    let mut n2: u64 = 0;
    let mut m2: u64 = 0;
    let mut n5: u64 = 0;
    let mut m5: u64 = 0;

    for (&key, &value) in &mprime {
        if key == 2 {
            n2 = nprime[&key];
            m2 = value;
        } else if key == 5 {
            n5 = nprime[&key];
            m5 = value;
        } else {
            if nprime[&key] < value {
                println!("-1");
                return;
            } else {
                ans *= (key as u64).pow((nprime[&key] - value) as u32) % 10;
            }
        }
    }

    if n2 < m2 {
        n5 += m2 - n2;
        n2 = m2;
    }
    if n5 < m5 {
        n2 += m5 - n5;
        n5 = m5;
    }
    ans *= 2u64.pow((n2 - m2) as u32) % 10;
    ans *= 5u64.pow((n5 - m5) as u32) % 10;
    while ans % 10 == 0 {
        ans /= 10;
    }

    println!("{}", ans % 10);
}