Problem:
Score : 300 points

Problem Statement

You are given a string S of length N and another string T of length M.
These strings consist of lowercase English letters.

A string X is called a good string when the following conditions are all met:

Let L be the length of X. L is divisible by both N and M.

Concatenating the 1-st, (\frac{L}{N}+1)-th, (2 \times \frac{L}{N}+1)-th, ..., ((N-1)\times\frac{L}{N}+1)-th characters of X, without changing the order, results in S.

Concatenating the 1-st, (\frac{L}{M}+1)-th, (2 \times \frac{L}{M}+1)-th, ..., ((M-1)\times\frac{L}{M}+1)-th characters of X, without changing the order, results in T.

Determine if there exists a good string. If it exists, find the length of the shortest such string.

Constraints

1 \leq N,M \leq 10^5

S and T consist of lowercase English letters.

|S|=N

|T|=M

Input

Input is given from Standard Input in the following format:

N M
S
T

Output

If a good string does not exist, print -1; if it exists, print the length of the shortest such string.

Sample Input 1

3 2
acp
ae

Sample Output 1

6

For example, the string accept is a good string.
There is no good string shorter than this, so the answer is 6.

Sample Input 2

6 3
abcdef
abc

Sample Output 2

-1

Sample Input 3

15 9
dnsusrayukuaiia
dujrunuma

Sample Output 3

45

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;


public class Main {
    public static void main(String[] args) {
      
        Scanner sc = new Scanner(System.in);
        int  count = sc.nextInt();
        int  count1 = sc.nextInt();
 String  line = sc.nextLine();
 String  line1 = sc.nextLine();
 String  line2 = sc.nextLine();
 String result = "";
 int n = Math.min(count,count1);
StringBuilder sb = new StringBuilder();
  for(int i =0;i<n;i++){
sb.append(line1.charAt(i)).append(line2.charAt(i));
result =sb.toString();
if(line1.charAt(i) == result.charAt(i+1)&&line1.charAt(i) == result.charAt(i+1)){
        line = String.valueOf(result.length());
       
  }
  else {
      line ="-1";
  }

}
  System.out.println(line);
  
         
        
    
        
    }
}