L,R,M,K = map(int,input().split())
ans = ""
if K == 0 or min(L,R) == 0:
  ans = "Yes"
elif R*K%M < M or L*K%M > M:
  if L*K < M:
    ans = "Yes" 
  else:
    ans = "No"
else:
  ans = "Yes"
print(ans)