#include <iostream>
#include <set>
using namespace std;
int main()
{
    int n;
    char c;
    set<char> st;
    cin >> n;
    while (n--)
    {
        c = getchar();
        if (c >= 'A' && c <= 'Z')
            c += 32;
        st.insert(c);
    }
    cout << (st.size() == 26 ? "YES" : "NO");
    return 0;
}

#17 wa