All Alphabets – Upper/Lower Case

The program must accept two string values S1 and S2 containing only alphabets as the input. The program must print yes if all the 26 alphabets (case insensitive) are present across the string values S1 and S2. Else the program must print no as the output.

Example Input/Output 1:
Input:
abcdEFGHIJk
LMNOpqrstuvwwxxxYYYzzz

Output:
yes

Explanation:
All the 26 alphabets (case insensitive) are present across the string values S1 and S2.
So yes is printed.