import sys sys.setrecursionlimit(10**7) def I(): return int(sys.stdin.readline().rstrip()) def MI(): return map(int,sys.stdin.readline().rstrip().split()) def LI(): return list(map(int,sys.stdin.readline().rstrip().split())) def LI2(): return list(map(int,sys.stdin.readline().rstrip())) def S(): return sys.stdin.readline().rstrip() def LS(): return list(sys.stdin.readline().rstrip().split()) def LS2(): return list(sys.stdin.readline().rstrip()) S = S() s = S[0] for t in S: if t != s: break else: if len(S) % 2 == 1: print(-1) else: print(0) exit() N = len(S) for i in range(N): if S[i] != S[N-1-i]: print(N) break else: print(N-2)