#include <bits/stdc++.h>
using namespace std;
struct alp {
  char bkv;
  int sk;
};
int main() {
  int n;
  string s;
  cin >> n >> s;
  for (int i = 0; i < n; i++) s[i] = tolower(s[i]);
  alp alp[26];
  int tt = 0;
  for (int i = 97; i <= 122; i++) {
    alp[tt].bkv = i;
    alp[tt].sk = 0;
    tt++;
  }
  for (int i = 0; i < n; i++)
    for (int j = 0; j < 26; j++)
      if (s[i] == alp[j].bkv) {
        alp[j].sk++;
        break;
      }
  for (int i = 0; i < 26; i++)
    if (alp[i].sk == 0) {
      cout << "NO";
      return 0;
    }
  cout << "YES";
  return 0;
}
