#include <bits/stdc++.h>
using namespace std;
void solve() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  for (long long i = 0; i < n; i += 1) {
    s[i] = tolower(s[i]);
  }
  int hash[26];
  memset(hash, 0, sizeof(hash));
  for (long long i = 0; i < n; i += 1) {
    hash[s[i] - 'a'] = 1;
  }
  int c = 0;
  for (long long i = 0; i < 26; i += 1) {
    if (hash[i]) c++;
  }
  cout << (c == 26 ? "YES" : "NO") << "\n";
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(NULL);
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
