from collections import Counter
x = input()
if len(x) >= 4:
    c = Counter(x)
    if len(c) == 1:
        print(-(len(x)%2))
    else:
        for i in range(len(x)//2):
            if x[i] != x[-i-1]:
                print(len(x))
                break
        else:
            print(len(x)-2)
else:
    if x[0] == x[-1]:
        print(-(len(x)%2))
    else:
        print(len(x))