The fewest bags of rice

You deliver exactly n kg of rice using 3 kg bags and 5 kg bags. Complete the function rice(n), which returns the smallest possible number of bags. If you cannot make exactly n kg, return -1. For 18 kg, three 5 kg bags and one 3 kg bag make 4 bags.

Starter code

def rice(n):
    # Write your code here
    pass

print(rice(18))