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* argv[]) {
    int n;
    char a[101], b[101], c[101];
    int min;
    int i;
    
    scanf("%d\n%s\n%s\n%s", &n, a, b, c);
    
    min = n*3;
    
    for(i=0; i<n; i++) {
    	if(a[i] == b[i]) {
    		min -= 2;
    		if(a[i] == c[i]) {
    			min--;
    		}
    	} else if(b[i] == c[i]) {
    		min -= 2;
    		if(b[i] == a[i]) {
    			min--;
    		}
    	} else if(c[i] == a[i]) {
    		min -= 2;
    		if(c[i] == b[i]) {
    			min--;
    		}
    	} else {
    		min--;
    	}
    }
    printf("%d\n", min);
    return 0;
}