#include <bits/stdc++.h>
using namespace std;
void uppercase(char& letter) { letter = toupper(letter); }
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  char EngChars[26] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I',
                       'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R',
                       'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
  bool flag[26] = {false, false, false, false, false, false, false,
                   false, false, false, false, false, false, false,
                   false, false, false, false, false, false, false,
                   false, false, false, false, false};
  int wordLength;
  cin >> wordLength;
  char* word;
  word = new char[wordLength];
  if (wordLength < 26) {
    for (int i = 0; i < wordLength; i++) {
      cin >> word[i];
    }
    cout << "NO";
  } else {
    for (int i = 0; i < wordLength; i++) {
      cin >> word[i];
      uppercase(word[i]);
      int j = 0;
      bool whileLoob = true;
      while (whileLoob) {
        if (word[i] == EngChars[j]) {
          if (flag[j] == false) {
            flag[j] = true;
            whileLoob = false;
          } else if (flag[j] == true) {
            whileLoob = false;
          }
        }
        j++;
        if (j > 26) {
          j = 0;
        }
      }
    }
    for (int i = 0; i < 26; i++) {
      if (flag[i] == false) {
        cout << "NO";
        return 0;
      }
    }
    cout << "YES";
  }
  return 0;
}
