#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long ans = 0;
  long long n;
  cin >> n;
  vector<long long> a(n), b(n), c(n);
  string s1, s2;
  cin >> s1 >> s2;
  for (long long i = 0; i < n; i++) {
    a[i] = (s1[i] == '0' ? 0 : 1);
  }
  for (long long i = 0; i < n; i++) {
    b[i] = (s2[i] == '0' ? 0 : 1);
    c[i] = a[i] ^ b[i];
  }
  for (long long i = 1; i < n; i++) {
    if (c[i] == 1 && c[i - 1] == 1 && (a[i] != a[i - 1])) {
      ans += 1;
      c[i] = 0;
      c[i - 1] = 0;
    }
  }
  for (long long i = 0; i < n; i++) {
    if (c[i] == 1) {
      ans += 1;
    }
  }
  cout << ans;
  return 0;
}
