#include <iostream>
#include <cmath>
#include <algorithm>
#include <vector>
#include <unordered_map>
using namespace std;
int main() {
    int N; string A, B, C; cin >> N >> A >> B >> C;
    string str = "";

    vector<int> count(10e3, 0);
    for (int i = 0; i < N; ++i) {
        int x, y, z; x = y = z = 0;
        if (A[i] == B[i]) x++;
        if (B[i] == C[i]) y++;
        if (A[i] == C[i]) z++;
        if (x >= y && x >= z) str += A[i];
        else if (y >= x && y >= z) str += B[i];
        else if (z >= y && z >= x) str += C[i];
    }
    int cnt = 0;
    for (int i = 0; i < N; ++i) {
        if (A[i] != str[i]) cnt++;
        if (B[i] != str[i]) cnt++;
        if (C[i] != str[i]) cnt++;
    }
    printf("%d\n", cnt);
}

#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<cmath>
#include<cstdio>
#include<queue>
#include<deque>
using namespace std;
typedef pair<int,int> ii;
typedef long long ll;
typedef pair<ll,ll> pll;
const int INF=1e9;
const ll MOD=1e9+7;

ll gcd(ll x,ll y){
    if(y==0) return 0;
    return gcd(y,x%y);
}

int dis2(int x1,int y1,int x2,int y2){
    return (x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
}

int main(){
    int n;cin>>n;
    string a,b,c;cin>>a>>b>>c;
    int ans=0;
    for(int i=0;i<n;i++){
        if(a[i]!=b[i]&&b[i]!=c[i]&&c[i]!=a[i]) ans+=2;
        else if(a[i]==b[i]&&b[i]==c[i]) continue;
        else ans++;
    }
    cout<<ans<<endl;
    return 0;
}