http://www.algospot.com/judge/problem/read/SENTENCE

계속 RTE 가 뜨는데.. 도저히 어디가 문제 인지 모르겠습니다..
고수님들 한번 도와주세요~

import java.util.Scanner;

public class Main {

    public static void main(String[] arg)
    {
        Scanner scan = new Scanner(System.in);

        int M=scan.nextInt();
        int N=scan.nextInt();

        int result=0;

        String[] Mstring=new String[M];
        String[] Nstring=new String[N];

        scan.nextLine();
        
        for(int i=0;i<M;i++)
        {
            Mstring[i]=scan.nextLine();
        }

        for(int i=0;i<N;i++)
        {
            Nstring[i]=scan.nextLine();
        }
        for(int i=0;i<M;i++)
        {
            for(int j=0;j<N;j++)
            {
                if(checkSame(Nstring[j],Mstring[i])==true)
                {
                    result++;
                }
            }   
        }

        System.out.println(result);
    }
    
    static boolean checkSame(String Nstring,String Mstring) // N is smaller
    {
        for(int i =0;i<Nstring.length();i++)
        {
            if(Nstring.charAt(i)!= Mstring.charAt(i))
            {
                return false;
            }
        }
        return true;
    }
}