import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")
debug = lambda x: sys.stderr.write(x+"\n")
writef = lambda x: print("{:.12f}".format(x))


s = input()
n = len(s)
if s==s[::-1]:
    if all((s[0]==s[i] for i in range(n))):
        if n%2==0:
            ans = 0
        else:
            ans = -1
    else:
        ans = n-2
else:
    ans = n
if ans==1:
    ans = -1
print(ans)