x1 = float(input("number? "))
x2 = float(input("number? "))
x3 = float(input("number? "))
x4 = float(input("number? "))
mx = x4

if x1 > mx:
    mx = x1
if x2 > mx:
    mx = x2
if x3 > mx:
    mx = x3

print("Maximum:", mx)