import sys



A, B, C, D = list(map(int, input().split()))

while A > 0 or B > 0:

    C = C - B

    if C <= 0:

        print("Yes")

        sys.exit()

    A = A - D

    if A <= 0:

        print("No")

        sys.exit()
A, B, C, D = list(map(int, input().split()))

while A > 0 or B > 0:

    C = C - B

    if C <= 0:

        print("Yes")

        break

    A = A - D

    if A <= 0:

        print("No")

        break
import sys

A, B, C, D = list(map(int, input().split()))
while A > 0 or B > 0:
    C = C - B
    if C <= 0:
        print("Yes")
        sys.exit()
    A = A - D
    if A <= 0:
        print("No")
        sys.exit()

A, B, C, D = list(map(int, input().split()))
while A > 0 or B > 0:
    C = C - B
    if C <= 0:
        print("Yes")
        break
    A = A - D
    if A <= 0:
        print("No")
        break

-import sys - -        sys.exit() +        break -        sys.exit() +        break