#include <bits/stdc++.h>
using namespace std;
int main() {
  char word;
  int i, l, count[27], flag, n;
  while (cin >> n) {
    flag = 0;
    memset(count, 0, sizeof(count));
    for (i = 0; i < n; i++) {
      cin >> word;
      if (word <= 122 && word >= 97)
        count[word - 96]++;
      else
        count[word - 64]++;
    }
    for (i = 1; i <= 26; i++) {
      if (count[i] == 0) {
        flag = 1;
        break;
      }
    }
    if (flag)
      cout << "NO\n";
    else
      cout << "YES\n";
  }
  return 0;
}
