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.io.PrintStream;
import java.util.Scanner;

public class Main {
    private static final PrintStream so = System.out;
    private static final Scanner     sc = new Scanner(System.in);

    public static void main(String[] args) {
        int n = sc.nextInt();
        String a = sc.next();
        String b = sc.next();
        String c = sc.next();
        int count = 0;
        for (int i = 0; i < n; i++) {
            char ai = a.charAt(i);
            char bi = b.charAt(i);
            char ci = c.charAt(i);
            if (ai == bi && bi == ci) {
                // do nothing
            } else if (ai != bi && bi != ci && ci != ai) {
                count += 2;
            } else {
                count += 1;
            }
        }
        so.println(count);
    }
}