#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 1000005;
ll fw[MAXN];
int n;
void update(int x, ll v){
while (x <= n){
fw[x] += v;
x += (x & (-x));
}
}
ll query(int x){
ll ans = 0;
while (x){
ans += fw[x];
x -= (x & (-x));
}
return ans;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n;
vector<int> pos[26], orig(n << 1);
for (int i = 0; i < (n << 1); i++){
char ch; cin >> ch;
orig[i] = ch - 'a';
pos[ch - 'a'].push_back(i);
}
vector<int> swvl, swvr;
vector<bool> issw(n << 1, 0);
for (int i = 0; i < 26; i++){
int sz = pos[i].size() >> 1;
for (int j = 0; j < sz; j++)
if (pos[i][j] >= n){
swvr.push_back(pos[i][j]);
issw[pos[i][j]] = 1;
}
for (int j = sz; j < (sz << 1); j++)
if (pos[i][j] < n){
swvl.push_back(pos[i][j]);
issw[pos[i][j]] = 1;
}
}
sort(swvl.begin(), swvl.end()); sort(swvr.begin(), swvr.end());
ll ans = 0, oop = swvl.size();
for (int i = 0; i < oop; i++) ans += (n - 1 - i) - swvl[oop - 1 - i];
for (int i = 0; i < oop; i++) ans += swvr[i] - (n + i);
ans += oop * oop;
vector<int> vl, vr;
for (int i = 0; i < n; i++) (issw[i] ? vr : vl).push_back(orig[i]);
for (int i = n; i < (n << 1); i++) (issw[i] ? vl : vr).push_back(orig[i]);
deque<int> dq[26];
for (int i = 0; i < n; i++) dq[vl[i]].push_back(i + 1);
for (int i = 0; i < n; i++){
int val = dq[vr[i]].front(); dq[vr[i]].pop_front();
ans += query(n) - query(val);
update(val, 1);
}
cout << ans;
}
