Problem:
Score : 300 points

Problem Statement

Takahashi loves the number 7 and multiples of K.

Where is the first occurrence of a multiple of K in the sequence 7,77,777,\ldots? (Also see Output and Sample Input/Output below.)

If the sequence contains no multiples of K, print -1 instead.

Constraints

1 \leq K \leq 10^6

K is an integer.

Input

Input is given from Standard Input in the following format:

K

Output

Print an integer representing the position of the first occurrence of a multiple of K. (For example, if the first occurrence is the fourth element of the sequence, print 4.)

Sample Input 1

101

Sample Output 1

4

None of 7, 77, and 777 is a multiple of 101, but 7777 is.

Sample Input 2

2

Sample Output 2

-1

All elements in the sequence are odd numbers; there are no multiples of 2.

Sample Input 3

999983

Sample Output 3

999982

Solution in Kotlin (1.3.71) (judge verdict: Wrong Answer)

fun main(args: Array<String>) {
    fun kake(r: Int): Int {
        return Math.pow(10.toDouble(), r.toDouble()).toInt()
    }

    val k = readLine()!!.toInt()

    if (7 % k == 0) {
        println(1)
    }

    var tmp = 7
    var base = 7
    for (i in 1..10) {
        tmp = tmp + (base * kake(i))
        println(tmp.toString())
        if (tmp % k == 0) {
            println(tmp)
            return
        }
    }
    println("-1")

}