# B - Battle



a, b, c, d = list(map(int, input().split()))



while c > 0 and a > 0:

    c -= b

    a -= d



print(('Yes' if c <= 0 else 'No'))
# B - Battle



import math



a, b, c, d = list(map(int, input().split()))



ao = math.ceil(c / b)  # 青木君の生存回数

ta = math.ceil(a / d)  # 高橋君の生存回数



print(('Yes' if ao <= ta else 'No'))

# B - Battle
a, b, c, d = list(map(int, input().split()))
while c > 0 and a > 0:
    c -= b
    a -= d
print(("Yes" if c <= 0 else "No"))

# B - Battle
import math

a, b, c, d = list(map(int, input().split()))
ao = math.ceil(c / b)  # 青木君の生存回数
ta = math.ceil(a / d)  # 高橋君の生存回数
print(("Yes" if ao <= ta else "No"))

+import math + -while c > 0 and a > 0: -    c -= b -    a -= d -print(("Yes" if c <= 0 else "No")) +ao = math.ceil(c / b)  # 青木君の生存回数 +ta = math.ceil(a / d)  # 高橋君の生存回数 +print(("Yes" if ao <= ta else "No"))