#include <bits/stdc++.h>
using namespace std;
int main() {
  int flag = 1;
  map<char, int> m1;
  char c = 'A';
  for (int i = 0; i < 26; i++) {
    m1.insert({c, 0});
    c++;
  }
  int n;
  cin >> n;
  string s1;
  char s2[n];
  cin >> s1;
  for (int i = 0; i < s1.size(); i++) {
    s2[i] = toupper(s1[i]);
  }
  for (int i = 0; i < n; i++) {
    for (auto itr = m1.begin(); itr != m1.end(); ++itr) {
      if (s2[i] == itr->first) {
        itr->second++;
      }
    }
  }
  for (auto itr = m1.begin(); itr != m1.end(); ++itr) {
    if (itr->second == 0) {
      flag = 0;
    }
  }
  if (flag == 0) {
    cout << "NO" << endl;
  } else
    cout << "YES" << endl;
}
