#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string x;
  cin >> x;
  int ans = 0;
  int count[100];
  memset(count, 0, sizeof(count));
  for (int i = 0; i < n; i++) {
    if (x[i] < 97) {
      x[i] += 32;
    }
    count[x[i] - 96]++;
  }
  for (int i = 1; i <= 26; i++) {
    if (count[i] > 0)
      ans = 1;
    else {
      ans = 0;
      break;
    }
  }
  if (ans == 1)
    cout << "YES\n";
  else
    cout << "NO\n";
}
