f = open('INPUT.TXT')
s = f.read().strip()
f.close()

def is_palindrome(string):
    return string == string[::-1]

result = ""

if not is_palindrome(s):
    result = s
elif len(s) > 1:
    if not is_palindrome(s[:-1]):
        result = s[:-1]
    elif not is_palindrome(s[1:]):
        result = s[1:]
    else:
        result = "NO SOLUTION"
else:
    result = "NO SOLUTION"

f = open('OUTPUT.TXT', 'w')
f.write(result)
f.close()