#include <bits/stdc++.h>
using namespace std;
int main() {
  long int n, c = 0, i;
  cin >> n;
  string s;
  cin >> s;
  if (n < 26) {
    cout << "NO" << endl;
  } else {
    for (i = 0; i < s.size(); i++) {
      if (s[i] >= 'A' && s[i] <= 'Z') {
        s[i] = s[i] + 32;
      }
    }
    sort(s.begin(), s.end());
    for (i = 0; i < s.size(); i++) {
      if (s[i] != s[i + 1]) {
        c++;
      }
    }
    if (c == 26) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }
  return 0;
}
