#include <bits/stdc++.h>
using namespace std;
vector<int> sort_cyclic_shifts(string const& s) {
  int n = s.size();
  const int alphabet = 256;
  vector<int> p(n), c(n), cnt(max(alphabet, n), 0);
  for (int i = 0; i < n; i++) cnt[s[i]]++;
  for (int i = 1; i < alphabet; i++) cnt[i] += cnt[i - 1];
  for (int i = n - 1; i >= 0; i--) p[--cnt[s[i]]] = i;
  c[p[0]] = 0;
  int classes = 1;
  for (int i = 1; i < n; i++) {
    if (s[p[i]] != s[p[i - 1]]) classes++;
    c[p[i]] = classes - 1;
  }
  vector<int> pn(n), cn(n);
  for (int h = 0; (1 << h) < n; ++h) {
    for (int i = 0; i < n; i++) {
      pn[i] = p[i] - (1 << h);
      if (pn[i] < 0) pn[i] += n;
    }
    fill(cnt.begin(), cnt.begin() + classes, 0);
    for (int i = 0; i < n; i++) cnt[c[pn[i]]]++;
    for (int i = 1; i < classes; i++) cnt[i] += cnt[i - 1];
    for (int i = n - 1; i >= 0; i--) p[--cnt[c[pn[i]]]] = pn[i];
    cn[p[0]] = 0;
    classes = 1;
    for (int i = 1; i < n; i++) {
      pair<int, int> cur = {c[p[i]], c[(p[i] + (1 << h)) % n]};
      pair<int, int> prev = {c[p[i - 1]], c[(p[i - 1] + (1 << h)) % n]};
      if (cur != prev) ++classes;
      cn[p[i]] = classes - 1;
    }
    c.swap(cn);
  }
  return p;
}
vector<int> suffix_array_construction(string s) {
  s += "$";
  vector<int> sorted_shifts = sort_cyclic_shifts(s);
  sorted_shifts.erase(sorted_shifts.begin());
  return sorted_shifts;
}
vector<int> lcp_construction(string const& s, vector<int> const& p) {
  int n = s.size();
  vector<int> rank(n, 0);
  for (int i = 0; i < n; i++) rank[p[i]] = i;
  int k = 0;
  vector<int> lcp(n - 1, 0);
  for (int i = 0; i < n; i++) {
    if (rank[i] == n - 1) {
      k = 0;
      continue;
    }
    int j = p[rank[i] + 1];
    while (i + k < n && j + k < n && s[i + k] == s[j + k]) k++;
    lcp[rank[i]] = k;
    if (k) k--;
  }
  return lcp;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n;
  string s, t;
  cin >> n >> s >> t;
  reverse(s.begin(), s.end());
  reverse(t.begin(), t.end());
  vector<int> p = suffix_array_construction(s);
  vector<int> lcp = lcp_construction(s, p);
  vector<int> new_lcp;
  int prev = -1;
  long long ans = 0;
  for (int i = 0; i < p.size(); i++) {
    if (t[p[i]] == '1') continue;
    ans = max(ans, (long long)p.size() - p[i]);
    if (prev != -1) {
      new_lcp.push_back(p.size());
      for (int j = prev; j < i; j++)
        new_lcp.back() = min(new_lcp.back(), lcp[j]);
    }
    prev = i;
  }
  vector<int> L(new_lcp.size()), R(new_lcp.size());
  for (int i = 0; i < new_lcp.size(); i++) {
    L[i] = i - 1;
    while (L[i] >= 0 and new_lcp[L[i]] >= new_lcp[i]) L[i] = L[L[i]];
  }
  for (int i = (int)new_lcp.size() - 1; i >= 0; i--) {
    R[i] = i + 1;
    while (R[i] < new_lcp.size() and new_lcp[R[i]] >= new_lcp[i])
      R[i] = R[R[i]];
  }
  for (int i = 0; i < new_lcp.size(); i++)
    ans = max(ans, new_lcp[i] * 1LL * (R[i] - L[i]));
  cout << ans << "\n";
}
