s = list(map(str,input()))
ans = len(s)
elem = set()
flag = True
for i in range(ans//2):
    if(s[i] != s[ans-1-i]):
        flag = False
        break
    else:
        elem.add(s[i])

if((ans % 2 != 0) & (ans // 2 > 0)):
    elem.add(s[i+1])
    
if(flag):
    if(len(elem) == 1):
        if(ans % 2 == 0):
            print(0)
        else:
            print(-1)
    else:
        if(ans == 3):
            print(-1)
        else:
            print(ans - 2)
else:
    print(ans)