2839. 설탕 배달

python
weight = int(input())
count = 0

if weight % 5 == 0:
    print(int(weight / 5))
else:
    while(True):
        count += 1
        weight -= 3

        if weight < 0:
            print(-1)
            break

        if weight == 0:
            print(count)
            break

        if weight % 5 == 0:
            print(count + int(weight / 5))
            break