[백준 2839] 설탕 배달

DP

n=int(input())

d=[5001]*5001

d[3]=1
d[5]=1

for i in range(6,n+1):
  if d[i-3]==5001:
    pass
  else:
    d[i]=min(d[i],d[i-3]+1)
  if d[i-5]==5001:
    pass
  else:
    d[i]=min(d[i],d[i-5]+1)

if d[n]==5001:
  print(-1)
else:
  print(d[n])