import math
from math import sqrt
import sys
from collections import deque, defaultdict
from heapq import heappop, heappush
from copy import deepcopy

INF=10**18
MOD=10**9+7
MAX=10**5+7

#N,K=map(int, input().split())
#A=list(map(int, input().split()))

def main():
  L,R,M,K=map(int, input().split())

  a=L*K
  b=R*K
  if (a-1)//M!=b//M:
    print("Yes")
  else:
    print("No")
  
if __name__ == '__main__':
    main()