import bisect import copy import decimal import fractions import heapq import itertools import math import random import sys import time from collections import Counter,deque,defaultdict from functools import lru_cache,reduce from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max def _heappush_max(heap,item): heap.append(item) heapq._siftdown_max(heap, 0, len(heap)-1) def _heappushpop_max(heap, item): if heap and item < heap[0]: item, heap[0] = heap[0], item heapq._siftup_max(heap, 0) return item from math import gcd as GCD read=sys.stdin.read readline=sys.stdin.readline readlines=sys.stdin.readlines write=sys.stdout.write #import pypyjit #pypyjit.set_param('max_unroll_recursion=-1') #sys.set_int_max_str_digits(10**9) S=readline().rstrip() if len(set(S))==1: if len(S)%2: ans=-1 else: ans=0 elif S!=S[::-1]: ans=len(S) else: if len(S)==3: ans=-1 else: ans=len(S)-2 print(ans)