T,S,D=map(int, input().split())
t=D/S
now=T
ans=0
for i in range(10000):
  if 18<=now<24 or now<6:
    tt=min(1,t)
    t-=tt 
    ans+=tt 
  else:
    tt=min(1,t)
    t-=tt
  now+=1
  now%=24
  if t==0:
    print(ans)
    exit()