def get_prefix(l,r,D):
if l == 0:
return D[r]
else:
return D[r] -D[l-1]
S = list(map(int,list(input())))
D = [S[0]]
for i in range(1,len(S)):
D.append(D[-1]+S[i])
Mx = 0
for ll in range(2,len(S)+1,2):
for start in range(0,len(S)-ll+1):
k = get_prefix(start,start+(ll//2)-1,D)
k2 = get_prefix(start+(ll//2),start+ll-1,D)
if k == k2:
Mx = ll
print(Mx)