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.*;
import java.util.*;
 
public class Main {
 
	void submit() {
	    int N = nextInt();
	    char[] A = nextString().toCharArray();
	    char[] B = nextString().toCharArray();
	    char[] C = nextString().toCharArray();
	    
	    int total_change = 0;
	    
	    for(int i=0; i<N; i++){
	        if(A[i] != B[i] && B[i] != C[i] && C[i] != A[i] ){
	            total_change+=2;	            
	        }else if(A[i] != B[i] || B[i] != C[i] ||  C[i] != A[i]){
	            total_change++;	            
	        }
	    }

        out.println(total_change);
	}

	void preCalc() {
 
	}
 
	void stress() {
 
	}
 
	void test() {
 
	}
 
	Main() throws IOException {
		br = new BufferedReader(new InputStreamReader(System.in));
		out = new PrintWriter(System.out);
		preCalc();
		submit();
		//stress();
		//test();
		out.close();
	}
 
	static final Random rng = new Random();
 
	static int rand(int l, int r) {
		return l + rng.nextInt(r - l + 1);
	}
 
	public static void main(String[] args) throws IOException {
		new Main();
	}
 
	BufferedReader br;
	PrintWriter out;
	StringTokenizer st;
 
	String nextToken() {
		while (st == null || !st.hasMoreTokens()) {
			try {
				st = new StringTokenizer(br.readLine());
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}
		return st.nextToken();
	}
 
	String nextString() {
		try {
			return br.readLine();
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}
 
	int nextInt() {
		return Integer.parseInt(nextToken());
	}
 
	long nextLong() {
		return Long.parseLong(nextToken());
	}
 
	double nextDouble() {
		return Double.parseDouble(nextToken());
	}
}