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)

import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int N = Integer.parseInt(in.nextLine());
		String A = in.nextLine();
		String B = in.nextLine();
		String C = in.nextLine();
		in.close();

		System.out.println(diff(A, B, C));
	}

	static int diff(String A, String B, String C) {
		int result = 0;
		for (int i = 0; i < A.length(); ++i) {
			char a = A.charAt(i);
			char b = B.charAt(i);
			char c = C.charAt(i);
			if (a == b && b == c && c == a) {

			} else if (a == b || b == c || c == a) {
				result++;
			} else {
				result = result + 2;
			}
		}
		return result;
	}

}