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 Perl (v5.18.2) (judge verdict: Accepted)

$ii = 0;
while(<STDIN>){
    $line[$ii] = $_;
	$ii++;
}

$N = $line[0];
$A = $line[1];
$B = $line[2];
$C = $line[3];

$Ans = 0;
for ($xx = 0; $xx < $N; $xx++) {
	$tmp = 2;
    $a = substr($A, $xx, 1);
    $b = substr($B, $xx, 1);
    $c = substr($C, $xx, 1);
    
   	if ($b eq $c) { $tmp = 1; }
   	if ($c eq $a) { $tmp = 1; }
   	if ($a eq $b) {
    	if ($b eq $c) {
    		$tmp = 0;
        } else {
    		$tmp = 1;
        }
    }
	$Ans += $tmp;
    
}

print "$Ans\n";