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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <algorithm>
#include <cstdio>
#include <iostream>
#include <string>
#define pq priority_queue
#define mp make_pair
#define cauto const auto &

#define REP(i, n) for (int i = 0, i##_len = (n); i < i##_len; ++i)
#define all(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())

#define clr(ar, val) memset(ar, val, sizeof(ar))

template <class T> bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T> bool chmin(T &a, const T &b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

using namespace std;

typedef long long int64;
typedef long long lint;
typedef long long lli;
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, int> pli;
typedef pair<int, ll> pil;
typedef pair<ll, ll> pll;

const int iinf = 1 << 29;
const long long linf = 1ll << 61;

int main() {
    int n;
    cin >> n;
    char a[n], b[n], c[n];
    scanf("%s", a);
    scanf("%s", b);
    scanf("%s", c);

    int ans=0;

    REP(i,n){
        if(a[i]==b[i] || a[i]==c[i] || c[i]==b[i]){
            if(a[i]==b[i] && b[i] == c[i]){
                continue;
            }
            ans+=1;
            continue;
        }
        ans+=2;
    }
    cout<<ans<<endl;
}