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.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int K = sc.nextInt();
		int A[];
        A=new int[100];
		double B[];
        B=new double[100];
        B[0]=7;
        double d;
        d=1.0;
        for(int i=1;i<100;i++){
            for(int j=0;j<i;j++){
              d=d*10.0;
            }
        	B[i]=B[i-1]+7.0*d;
        }
        for(int i=0;i<100;i++){
        	A[i]=(int)B[i];
        }        
        int C[];
        int ff;
        ff=0;
        C=new int[100];
        for(int i=0;i<100;i++){
        	C[i]=A[i]%K;
            if (C[i]==0){
                ff=1;
            	System.out.println(i);
                break;
            }
        }
       if(ff==0){
       System.out.println(-1);
       }
	}
}