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 Fortran (gfortran v4.8.4) (judge verdict: Accepted)

program main
implicit None
	integer(8)::n,p=0,i
	character(len =100)::a,b,c
	
	read*,n
	read*,a,b,c
	
	do i = 1,n
		if(a(i:i) == b(i:i))then
			if(a(i:i) /= c(i:i)) p = p+1
			else
				if(a(i:i) == c(i:i))then
					p = p+1
					else if(b(i:i) == c(i:i))then
					p = p+1
					else
					p = p+2
				endif
		endif
	enddo
	
	print "(i0)",p
end program main