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 Python (3.4.3) (judge verdict: Accepted)

# 2019/01/27
# NIKKEI Programming Contest 2019 - B

# Input
n = int(input())
a = input()
b = input()
c = input()
sum = 0

# Choose Max
for idx in range(n):
    
    if a[idx] == b[idx]:
        if a[idx] == c[idx]:
            # All chars are same
            sum += 0
        else:
            # a=b, a!=c
            sum += 1
    else:
        if a[idx] == c[idx]:
            # a!=b, a=c
            sum += 1
        else:
            if b[idx] == c[idx]:
                # a!=b, b=c
                sum += 1
            else:
                # All chars are different
                sum += 2
# Output
print(sum)