from collections import deque
s = deque(map(str,input()))
ans = len(s)
flag = True
while(1):
    if(ans > 1):
        for i in range(ans//2):
            if(s[i] != s[ans-1-i]):
                flag = False
                break
        if(flag):
            s.pop()
            s.pop()
            ans -= 2
        else:
            print(ans)
            exit(0)
    elif(ans == 1):
        print(-1)
        exit(0)
    else:
        print(0)
        exit(0)