c = input()
if c.isupper():
    n = ord(c) - 65
else:
    n = ord(c) - 97
ans = [] 
for i in range(n + 1):
    if i % 2 == 0:
        ans.append(chr(65 + i))
    else:
        ans.append(chr(97 + i))
ans += ans[:-1][::-1]
print(''.join(ans))