with open("b.txt", "r") as file:
    num_this = 0
    is_subsequence = True
    lines = file.readlines()
    num_prev = int(lines[0].replace("\n", ""))
    for i in range(1, len(lines)):
        num_this = int(lines[i].replace("\n", ""))
        is_subsequence = ((num_prev>0)and(num_this<0))or((num_prev<0)and(num_this>0))and(is_subsequence)
        num_prev = int(lines[i].replace("\n", ""))
    
print(is_subsequence)