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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;
class Program
{
    static void Main(string[] args)
    {
        // 整数の入力
        int N = int.Parse(Console.ReadLine());
        string A = Console.ReadLine();
        string B = Console.ReadLine();
        string C = Console.ReadLine();


        int cnt = 0;

        // Aにそろえる
        for (int i = 0; i < N; i++)
        {
            //AとBとCが一致する
            if(A[i].Equals(B[i]) && A[i].Equals(C[i]))
            {
            }
            //AとBが一致する、Cが一致しない
            else if (A[i].Equals(B[i]) && !A[i].Equals(C[i]))
            {
                cnt++;
            }
            //AとCが一致する、Bが一致しない
            else if (A[i].Equals(C[i]) && !A[i].Equals(B[i]))
            {
                cnt++;
            }
            //BとCが一致する、Aが一致しない
            else if (B[i].Equals(C[i]) && !B[i].Equals(A[i]))
            {
                cnt++;
            }
            else
            {
                cnt += 2;
            }
        }

        //出力
        Console.WriteLine(cnt);
    }
}