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 (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
#include<string.h>

int main(int argc, char const *argv[])
{
	char A[100],B[100],C[100],base[100];
	int N;
	int i,j;
	int change_num=0;
	int num=0;
	scanf("%d%s%s%s",&N,A,B,C);

	for(i=0;i<N;i++)
	{
		for(j=0;j<2;j++)
		{
			if(A[i]==B[i]||A[i]==C[i])
			{
				base[i]=A[i];
			}
			else if(B[i]==C[i])
			{
				base[i]=B[i];
			}
			else
			{
				base[i]=A[i];
			}
		}
	}
	for(i=0;i<N;i++)
	{
		if(A[i]!=base[i])
		{
			change_num++;
		}
		if(B[i]!=base[i])
		{
			change_num++;
		}
		if(C[i]!=base[i])
		{
			change_num++;
		}
	}
	printf("%d\n",change_num);
	return 0;
}