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 Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.util.*;
 
class Main{
  public static void main(String[] args){
  	Scanner sc = new Scanner(System.in);
 	 long K = sc.nextInt();
 	 long R = -1;
	 long Ar = 7;
     long i=1;
    if(K%2!=0){
	 while(i<=K){
   	 	if(Ar%K == 0){
    	  R = i;
          i = K+1;
        }else{
    	  Ar+= 7*Math.pow(10,i);
          i++;
    	}
	  }
    }
  	  System.out.println(R);
  }
}