#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;
}
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