#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#define pb push_back
#define mp make_pair

ll func(char a, char b, char c, char d){
	if(a == b){
		if((c != d) && (c != a) && (d != a)){//cout << "ok\n";
			return 2;
		}
		
		else if((c != d) && ((c == a) || (d == a))){
			return 1;
		}
		
		else if(c == a && d == a)
		return 0;
		
		else if((c == d) && (c != a))
		return 0;
	}
	
	else{
		if((c != d) && (c != a) && (c != b) && (d != a) && (d != b))
		return 2;
		
		else if((c != d) && (((c == a) && (d == b)) || ((c == b) && (d == a))))
		return 0;
		
		else if((c != d) && ((c == a) || (c == b) || (d == a) || (d == b)))
		return 1;
		
		else if((c == d) && ((c == a) || (c == b)))
		return 1;
		
		else if((c == d) && ((c != a) && (c != b)))
		return 1;
	}
	return 0;
}

int main() {
	ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    
    int n;
    cin >> n;
    string a, b;
    cin >> a >> b;
    //cout << func('a', 'a', 'c', 'b') << endl;
    ll ans = 0;
    for(int i = 0, j = n-1; i <= j; i++, j--){//cout << i << " " << j << endl;
            if(i == j){
            	if(a[i] != b[i])
            	ans++;
            }
            else
    	ans += func(a[i], a[j], b[i], b[j]);
    //	cout << ans << endl;
    }
    
    cout << ans;
	return 0;
}