doctor fee calculation in python

1age=[]
2for i in range(20):
3    n=input()
4    if(n == ""):
5        break
6    elif(int(n) in range(0,120)):
7        age.append(int(n))
8    else:
9        print("invalid input")
10        exit()
11fee=0 
12for i in age:
13    if i in range(1,17):
14        fee =fee+200
15    elif(i in range(18,40)):
16        fee=fee+400
17    else:
18        fee=fee+300
19print(fee)