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<stdlib.h>
#include<string.h>

int main(){
    int num, i,count=0;
    char *str_a,*str_b,*str_c;

    scanf("%d",&num);

    str_a = (char*)malloc(sizeof(char)*num+1);
    str_b = (char*)malloc(sizeof(char)*num+1);
    str_c = (char*)malloc(sizeof(char)*num+1);

    scanf("%s",str_a);
    scanf("%s",str_b);
    scanf("%s",str_c);

    for(i=0;i<num;++i){
        if(str_a[i]==str_b[i] && str_a[i]==str_c[i]){
            continue;
        }else if(str_a[i]==str_b[i]){
            str_c[i]=str_b[i];
            count++;
        }else if(str_b[i]==str_c[i]){
            str_a[i]=str_b[i];
            count++;
        }else if(str_c[i]==str_a[i]){
            str_b[i]=str_c[i];
            count++;
        }else{
            str_b[i]=str_a[i];
            i--;
            count++;
        }
    }
    printf("%d",count);
    return 0;
}