#include <bits/stdc++.h>
using namespace std;
int ok[26];
int main(int argc, char const *argv[]) {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int total = 0;
  memset(ok, 0, sizeof ok);
  for (int i = 0; i < s.size(); i++) {
    if (s[i] >= 'a') {
      int cur = s[i] - 'a';
      if (!ok[cur]) {
        ok[cur] = 1;
        total++;
      }
    } else {
      int cur = s[i] - 'A';
      if (!ok[cur]) {
        ok[cur] = 1;
        total++;
      }
    }
  }
  if (total == 26) {
    cout << "YES" << endl;
  } else {
    cout << "NO" << endl;
  }
  return 0;
}
