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 <bits/stdc++.h>
#include <iostream>
using namespace std;
 
int main()
{ 
    long long int  n=0, temp=0, count=-1;
    cin>>n;
    temp=7;
    if(temp==1 || temp== 7){
        cout<<"1"<<endl;
        return 0;
    }
    for(int i=1;i<=10000000;i++){
        if(temp==0){
            count=i;
            break;
        }
        temp=(temp*10)+7;
        temp=temp%n;
    }
    cout<<count<<endl;
}