try:
  from icecream import ic
except:
  pass

def minuteToTime(n):
  return f"{str(n//60).zfill(2)}:{str(n%60).zfill(2)}"

def main():
  l,r,m=map(int,input().split())
  ans=set()
  for i in range(l,min(l+m+1,r+1)):
    ans.add(i%m)
  print(len(ans))
if __name__=="__main__":
  main()