def hailstone(p):
    """Takes input and continues to put in output if even does p//2 if odd 3p+1"""
    H = []
    while p != 1:
            H.append(p)
            if p > 0:
                if p%2 == 0:
                    p = p//2
                elif p%2 == 1:
                    p = 3*p+1
            else:
                return("Invalid Input")
    if p == 1:
        H.append(1)
    return(H)


print("Problem 1")
print(hailstone(1))

print("Problem 2")
print(hailstone(27))

print("problem 3")
maxLength = 0
for n in range(1, 20001):
    l = hailstone(n)
    m = len(l)
    if m > maxLength:
        maxLength = m
        largestInteger = n
print(largestInteger, maxLength)