#include <bits/stdc++.h>
using namespace std;
int diff(string a, string b) {
  if (a == b) return 0;
  if (a[0] == b[0] || a[1] == b[1]) return 1;
  return 2;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int format;
  cin >> format;
  string time;
  cin >> time;
  string h, m;
  h = time[0];
  h = h + time[1];
  m = time[3];
  m = m + time[4];
  string arr[12] = {"01", "02", "03", "04", "05", "06",
                    "07", "08", "09", "10", "11", "12"};
  string arr2[24] = {"00", "01", "02", "03", "04", "05", "06", "07",
                     "08", "09", "10", "11", "12", "13", "14", "15",
                     "16", "17", "18", "19", "20", "21", "22", "23"};
  string ans;
  if (format == 12) {
    string temp;
    int wawa = 3;
    for (int i = 0; i < 12; i++) {
      if (diff(h, arr[i]) < wawa) {
        wawa = diff(h, arr[i]);
        temp = arr[i];
      }
    }
    ans = temp;
    if (m[0] != '0' && m[0] != '1' && m[0] != '2' && m[0] != '3' &&
        m[0] != '4' && m[0] != '5')
      m[0] = '1';
    ans = ans + ':';
    ans = ans + m;
  } else {
    string temp;
    int wawa = 3;
    for (int i = 0; i < 24; i++) {
      if (diff(h, arr2[i]) < wawa) {
        wawa = diff(h, arr2[i]);
        temp = arr2[i];
      }
    }
    ans = temp;
    if (m[0] != '0' && m[0] != '1' && m[0] != '2' && m[0] != '3' &&
        m[0] != '4' && m[0] != '5')
      m[0] = '1';
    ans = ans + ':';
    ans = ans + m;
  }
  cout << ans;
  return 0;
}
