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 JavaScript (node.js v5.12) (judge verdict: Accepted)

// parameter "input" gets all data
function Main(input) {
	// the first line is assigned to input[0], the second line is assigned to input[1] similarly.
	var splitInput = input.split("\n");
	var n = (splitInput[0])
	var a = (splitInput[1])
	var b = (splitInput[2])
	var c = (splitInput[3])
	
	var result = 0
	
	for (var i=0; i<n; i++){
		if (a[i] == b[i] && a[i] == c[i]) {
			result += 0
		} else if (a[i] == b[i] || a[i] == c[i] || c[i] == b[i]) {
			result += 1
		} else {
			result += 2
		}
	}
	
	//output
	console.log('%d',result);
}
// Don't edit this line!
Main(require("fs").readFileSync("/dev/stdin", "utf8"));