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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include <stdio.h>

int main()
{
    int count;
    char x[100];
    char y[100];
    char z[100];
    int i;
    int tmp = 0;
    scanf("%d", &count);
    scanf("%s", x);
    scanf("%s", y);
    scanf("%s", z);

    for (i = 0; i < count; i++)
    {
        if (x[i] != y[i] && x[i] != z[i])
        {
            y[i] = x[i];
            tmp++;
            z[i] = x[i];
            tmp++;
        }
        if (x[i] != y[i])
        {
            if (y[i] == z[i])
            {
                x[i] = y[i];
                tmp++;
            }
        }
        if (x[i] != z[i])
        {
            if (x[i] == y[i])
            {
                z[i] = x[i];
                tmp++;
            }
        }
        if (y[i] != z[i])
        {
            if (x[i] == y[i])
            {
                z[i] = x[i];
                tmp++;
            }
        }
    }
    printf("%d\n", tmp);
}