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 Java7 (OpenJDK 1.7.0) (judge verdict: Accepted)

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

class Main{
    public static void main(String args[]) throws IOException {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String s1 = new String(in.readLine());
        String s2 = new String(in.readLine());
        String s3 = new String(in.readLine());
        String s4 = new String(in.readLine());

        int n = Integer.parseInt(s1);

        int score = 0;
        char c2,c3,c4;
        for( int x = 0; x < n ; x++){
            c2 = s2.charAt(x);
            c3 = s3.charAt(x);
            c4 = s4.charAt(x);

            if( c2 != c3 ){
                if( c2 != c4){
                    if( c3 != c4){
                        score = score + 2;
                    }else{
                        score = score + 1;
                    }
                }else{
                    score = score + 1;
                }
            }else{
                if( c2 != c4){
                    score = score + 1;
                }
            }
        }
        System.out.print( score );
  }
}