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.*;
public class Main {
	public static void main(String[] args) {
		try {
	        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
	        int n = Integer.parseInt(in.readLine());
	        String A = new String(in.readLine());
	        String B = new String(in.readLine());
	        String C = new String(in.readLine());
	        char[] charA = new char[n];
			char[] charB = new char[n];
			char[] charC = new char[n];
			charA = A.toCharArray();
			charB = B.toCharArray();
			charC = C.toCharArray();
			
			int ret = 0;
			for (int i = 0; i < n; i++) {
				if (charA[i] != charB[i] && charA[i] != charC[i] && charB[i] != charC[i] ) {
					ret = ret + 2;
				} else if (charA[i] != charC[i] || charA[i] != charB[i]) {
					ret++;
				}
			}
			System.out.println(String.valueOf(ret));

		} catch (Exception ex) {}
	}	
}