#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define SZ(v) ((int)(v.size()))
int freq[30];
void run () {
    int n;
    cin >> n;
    string s;
    cin >> s;
    for (int i = 0; i < n; ++i) {
        if (isupper(s[i]))
            s[i] += 32;
        freq[s[i] - 'a']++;
    }
    for (int i = 0; i < 26; ++i) {
        if (!freq[i]) {
            cout << "NO\n";
            return;
        }
    }
    cout << "YES\n";
}
int main () {
    int tt;
    tt = 1;
//    cin >> tt;
    while (tt--)
        run();
    return 0;
}