#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, i;
  char s[105];
  while (cin >> a) {
    getchar();
    gets(s);
    int hit[125] = {0}, flag = -1;
    for (i = 0; i < a; i++) {
      if (s[i] <= 90) s[i] = s[i] + 32;
      hit[s[i]] = 1;
    }
    for (i = 97; i <= 122; i++)
      if (hit[i] == 0) {
        flag = 1;
        break;
      }
    if (flag > 0)
      cout << "NO" << endl;
    else
      cout << "YES" << endl;
  }
}
