백준 [ALGORITHM] - 거스름돈 (14916)

count = 0

def change(n, count):

    if n < 0 or n == 1 or n == 3:
        return -1 

    while n > 0:
        if n < 0:
            break

        if n % 5 == 0:
            count += n // 5
            break
        
        else:
            n -= 2
            count += 1


    return count
pay = int(input())
count = change(pay, count)

print(count)