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: Runtime Error)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) {

		BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
		String inStr = "";
		try {
			inStr = new String(input.readLine());
		} catch (IOException e) {
			e.printStackTrace();
		}
		String[] inStrArray = inStr.split(" ");

		int N = Integer.valueOf(inStrArray[0]);
		String A = inStrArray[1];
		String B = inStrArray[2];
		String C = inStrArray[3];

		exec(N, A, B, C);

	}

	private static void exec(int _N, String _A, String _B, String _C) {

		int cnt = 0;
		for (int i = 0; i < _N; i++) {
			String tmpA = _A.substring(i, i+1);
			String tmpB = _B.substring(i, i+1);
			String tmpC = _C.substring(i, i+1);
			if (tmpA.equals(tmpB)) {
				if (!tmpA.equals(tmpC)) {
					// C入れ替える
					cnt++;
				}
			} else {
				if (tmpA.equals(tmpC)) {
					// Bを入れ替える
					cnt++;
				} else {
					if (tmpB.equals(tmpC)) {
						// Aを入れ替える
						cnt++;
					} else {
						// BとCを入れ替える
						cnt++;
						cnt++;
					}
				}
			}
		}

		System.out.println(cnt);
	}
}