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 C (GCC 9.2.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int main()
{
int no;
long s=7;
int cnt=1;
scanf("%d",&no);
if(no%2==0 || no%5==0){
  printf("-1");
}
else{
  while(1){
    if(s%no==0){
      printf("NO is: %d\n",s);
      printf("%d",cnt);
      break;
    }
    else if(cnt>no){
      printf("-1");
      break;
    }
    else{
      s=(s*10)+7;
      cnt++;
    }
  }
  
}
}