#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int i, j;
  int count = 0;
  if (s.length() < 26) {
    cout << "NO";
  } else {
    for (i = 0; i < s.length(); i++) {
      if (s[i] < 91) {
        s[i] += 32;
      }
    }
    for (i = 0; i < s.length(); i++) {
      for (j = i + 1; j < s.length(); j++) {
        if (s[i] == s[j]) {
          while (s[i] == s[j]) {
            s.erase(j, 1);
          }
        }
      }
    }
    for (i = 0; i < s.length(); i++) {
      count += s[i];
    }
    if (count == 2847) {
      cout << "YES";
    } else {
      cout << "NO";
    }
  }
}
