s="ABCDEFGHIJKLMNOPQRSTUVWXYZ" a=[s[:x]+s[x::-1]for x in range(26)] print('\n'.join(a+a[24::-1]))
Standard input is empty
A ABA ABCBA ABCDCBA ABCDEDCBA ABCDEFEDCBA ABCDEFGFEDCBA ABCDEFGHGFEDCBA ABCDEFGHIHGFEDCBA ABCDEFGHIJIHGFEDCBA ABCDEFGHIJKJIHGFEDCBA ABCDEFGHIJKLKJIHGFEDCBA ABCDEFGHIJKLMLKJIHGFEDCBA ABCDEFGHIJKLMNMLKJIHGFEDCBA ABCDEFGHIJKLMNONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWXWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWXYXWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWXYZYXWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWXYXWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWXWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPONMLKJIHGFEDCBA ABCDEFGHIJKLMNONMLKJIHGFEDCBA ABCDEFGHIJKLMNMLKJIHGFEDCBA ABCDEFGHIJKLMLKJIHGFEDCBA ABCDEFGHIJKLKJIHGFEDCBA ABCDEFGHIJKJIHGFEDCBA ABCDEFGHIJIHGFEDCBA ABCDEFGHIHGFEDCBA ABCDEFGHGFEDCBA ABCDEFGFEDCBA ABCDEFEDCBA ABCDEDCBA ABCDCBA ABCBA ABA A