Problem:
Score : 200 points

Problem Statement

You are given three strings A, B and C. Each of these is a string of length N consisting of lowercase English letters.

Our objective is to make all these three strings equal. For that, you can repeatedly perform the following operation:

Operation: Choose one of the strings A, B and C, and specify an integer i between 1 and N (inclusive). Change the i-th character from the beginning of the chosen string to some other lowercase English letter.

What is the minimum number of operations required to achieve the objective?

Constraints

1 \leq N \leq 100

Each of the strings A, B and C is a string of length N.

Each character in each of the strings A, B and C is a lowercase English letter.

Input

Input is given from Standard Input in the following format:

N
A
B
C

Output

Print the minimum number of operations required.

Sample Input 1

4
west
east
wait

Sample Output 1

3

In this sample, initially A = west、B = east、C = wait. We can achieve the objective in the minimum number of operations by performing three operations as follows:

Change the second character in A to a. A is now wast.

Change the first character in B to w. B is now wast.

Change the third character in C to s. C is now wast.

Sample Input 2

9
different
different
different

Sample Output 2

0

If A, B and C are already equal in the beginning, the number of operations required is 0.

Sample Input 3

7
zenkoku
touitsu
program

Sample Output 3

13

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

//package AtCoder.Nekkei;

import java.io.*;
import java.util.*;

class Main {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        int n = s.nextInt();
        char[][] arr = new char[3][n];
        for (int i = 0; i < 3; i++) {
            String str = s.next();
            arr[i] = str.toCharArray();
        }

        int sum = 0;
        for (int i = 0; i < n; i++) {
//            TreeSet<pair> set = new TreeSet<>();
//            if(set.)
//            set.add(new pair())
            HashSet<Character> set = new HashSet<>();
            set.add(arr[0][i]);
            set.add(arr[1][i]);
            set.add(arr[2][i]);

            sum += set.size() - 1;
        }
        System.out.println(sum);


    }


}