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.Collections.Generic;
using System.Linq;
using System.Runtime.Remoting.Messaging;
using System.Text;
using System.Threading.Tasks;

namespace NikkeiPGKing
{
    class Program
    {
        static void Main(string[] args)
        {
            Problem2.Problem2Read();
        }


    }
      public sealed class Problem2
    {
        public static void Problem2Read()
        {
            Console.ReadLine();
            string a = Console.ReadLine();
            string b = Console.ReadLine();
            string c = Console.ReadLine();
            Console.WriteLine( Problem2Solve(a , b, c));
        }

        public static int Problem2Solve(string a, string b, string c)
        {
            int cnt = 0;
            for (int i = 0; i < a.Length; i++)
            {
                cnt += DiffSteps(a[i], b[i], c[i]);
            }

            return cnt;
        }

        public static int DiffSteps(char a, char b, char c)
        {
            if (a == b && b == c)
            {
                return 0;
            }

            if (a == b || b == c || c == a)
            {
                return 1;
            }

            return 2;
        }

    }
}