#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < (n); i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;
const int INF = 1001001001;
const ll LINF = 1001002003004005006ll;
//const int mod = 1000000007;
//const int mod = 998244353;

int main()
{
  ll n;
  string s, t;
  cin >> n >> s >> t;
  int ans = 0;
  rep(i, 0, n) if (s[i] != t[i]) ans++;
  if (ans&1) ans = INF;
  int res = 0;
  reverse(s.begin(), s.end());
  rep(i, 0, n) if (s[i] != t[i]) res++;
  if (res%2 == 0) res = INF;
  cout << min(ans, res) << endl;
  return 0;
}