#include <bits/stdc++.h>
using namespace std;
long long cnt;
int const M = 1e6 + 1;
int x = INT_MIN;
int Vis[27];
int main() {
  int n, flag = 0;
  cin >> n;
  string s;
  cin >> s;
  for (int i = 0; i < s.length(); ++i) {
    s[i] = tolower(s[i]);
    Vis[s[i] - 'a'] = 1;
  }
  for (int i = 0; i < 26; ++i)
    if (Vis[i] == 0) {
      flag = 1;
      break;
    }
  (flag == 1) ? cout << "NO" << endl : cout << "YES" << endl;
}
