fun main(args: Array<String>) {
    val n = readLine()!!.toLong()
    val m = readLine()!!.toLong()
    val ans = div(n, m)
    println(ans)
}

val dic = mutableMapOf<Long, Boolean>()

fun div(n:Long, m:Long): Int {
    dic[n]?.let { return -1 }
    dic[n] = true
    if(n < m) {
        return div(n*10, m)
    }
    var ans = n / m
    if(n % m > 0) {
        return div(n%m, m)
    }
    while (ans % 10 == 0.toLong()) {
        ans = ans / 10
    }
    return (ans % 10).toInt()
}