import itertools
def submatrix(matrix, y_subset, x_subset):
    new_matrix=[]
    for array in matrix:
        new_matrix.append(array[x_subset[0] : x_subset[1]])
    return new_matrix[y_subset[0] : y_subset[1]]
sor=input()
szavak, current_distance=[list(format(ord(x), 'b')) for x in sor], 0
for i in range(len(szavak)):
    for j in range(len(szavak[0])):
        szavak[i][j]=int(szavak[i][j])
y, x= list(range(len(szavak))), list(range(len(szavak[0])))
for y_subset in itertools.combinations(y, 2):
    for x_subset in itertools.combinations(x, 2):
        if y_subset[1]-y_subset[0] == x_subset[1]-x_subset[0]:
            if(sum(sum(submatrix(szavak, y_subset, x_subset),[])) == (y_subset[1]-y_subset[0])*(y_subset[1]-y_subset[0]) or sum(sum(submatrix(szavak, y_subset, x_subset),[])) == 0):
                current_distance=max(current_distance, y_subset[1]-y_subset[0])
print(current_distance)