#include <iostream>
using namespace std;

string a;
int  c, b[27];



///////////////////////////////////////////////////////
int main()                                          //
{
    cin >> c >> a;

    for(int i = 0; i  < c; i++)
    {
       if(a[i] == 'a') b[0] = 1;
       if(a[i] == 'b') b[1] = 1;
       if(a[i] == 'c') b[2] = 1;
       if(a[i] == 'd') b[3] = 1;
       if(a[i] == 'e') b[4] = 1;
       if(a[i] == 'f') b[5] = 1;
       if(a[i] == 'g') b[6] = 1;
       if(a[i] == 'h') b[7] = 1;
       if(a[i] == 'i') b[8] = 1;
       if(a[i] == 'j') b[9] = 1;
       if(a[i] == 'k') b[10] = 1;
       if(a[i] == 'l') b[11] = 1;
       if(a[i] == 'm') b[12] = 1;
       if(a[i] == 'n') b[13] = 1;
       if(a[i] == 'o') b[14] = 1;
       if(a[i] == 'p') b[15] = 1;
       if(a[i] == 'q') b[16] = 1;
       if(a[i] == 'r') b[17] = 1;
       if(a[i] == 's') b[18] = 1;
       if(a[i] == 't') b[19] = 1;
       if(a[i] == 'u') b[20] = 1;
       if(a[i] == 'v') b[21] = 1;
       if(a[i] == 'w') b[22] = 1;
       if(a[i] == 'x') b[23] = 1;
       if(a[i] == 'y') b[24] = 1;
       if(a[i] == 'z') b[25] = 1;

       if(a[i] == 'A')b[0] = 1;
       if(a[i] == 'B')b[1] = 1;
       if(a[i] == 'C')b[2] = 1;
       if(a[i] == 'D')b[3] = 1;
       if(a[i] == 'E')b[4] = 1;
       if(a[i] == 'F')b[5] = 1;
       if(a[i] == 'G')b[6] = 1;
       if(a[i] == 'H')b[7] = 1;
       if(a[i] == 'I')b[8] = 1;
       if(a[i] == 'J')b[9] = 1;
       if(a[i] == 'K')b[10] = 1;
       if(a[i] == 'L')b[11] = 1;
       if(a[i] == 'M')b[12] = 1;
       if(a[i] == 'N')b[13] = 1;
       if(a[i] == 'O')b[14] = 1;
       if(a[i] == 'P')b[15] = 1;
       if(a[i] == 'Q')b[16] = 1;
       if(a[i] == 'R')b[17] = 1;
       if(a[i] == 'S')b[18] = 1;
       if(a[i] == 'T')b[19] = 1;
       if(a[i] == 'U')b[20] = 1;
       if(a[i] == 'V')b[21] = 1;
       if(a[i] == 'W')b[22] = 1;
       if(a[i] == 'X')b[23] = 1;
       if(a[i] == 'Y')b[24] = 1;
       if(a[i] == 'Z')b[25] = 1;
    }


    for(int i = 0; i < 26; i++) if(b[i] == 0){ cout << "NO"; return 0;}
    cout << "YES";
}