from math import floor,ceil,sqrt,factorial,log

from collections import Counter, deque

from functools import reduce

import numpy as np

def S(): return eval(input())

def I(): return int(eval(input()))

def MS(): return list(map(str,input().split()))

def MI(): return list(map(int,input().split()))

def FLI(): return [int(i) for i in input().split()]

def LS(): return list(MS())

def LI(): return list(MI())

def LLS(): return [list(map(str, l.split() )) for l in eval(input())]

def LLI(): return [list(map(int, l.split() )) for l in eval(input())]

def LLSN(n: int): return [LS() for _ in range(n)]

def LLIN(n: int): return [LI() for _ in range(n)]



A,B,C,D = MI()



t = A

a = C



for i in range(100):

    a -= B

    if a <= 0:

        print("Yes")

        exit()

    

    t -= D

    if t <= 0:

        print("No")

        exit()

from math import floor,ceil,sqrt,factorial,log

from collections import Counter, deque

from functools import reduce

# import numpy as np

def S(): return eval(input())

def I(): return int(eval(input()))

def MS(): return list(map(str,input().split()))

def MI(): return list(map(int,input().split()))

def FLI(): return [int(i) for i in input().split()]

def LS(): return list(MS())

def LI(): return list(MI())

def LLS(): return [list(map(str, l.split() )) for l in eval(input())]

def LLI(): return [list(map(int, l.split() )) for l in eval(input())]

def LLSN(n: int): return [LS() for _ in range(n)]

def LLIN(n: int): return [LI() for _ in range(n)]



A,B,C,D = MI()



x = -(-A//D)

y = -(-C//B)



if x >= y:

    print("Yes")

else:

    print("No")



# for i in range(100):

#     a -= B

#     if a <= 0:

#         print("Yes")

#         exit()

    

#     t -= D

#     if t <= 0:

#         print("No")

#         exit()

from math import floor, ceil, sqrt, factorial, log
from collections import Counter, deque
from functools import reduce
import numpy as np


def S():
    return eval(input())


def I():
    return int(eval(input()))


def MS():
    return list(map(str, input().split()))


def MI():
    return list(map(int, input().split()))


def FLI():
    return [int(i) for i in input().split()]


def LS():
    return list(MS())


def LI():
    return list(MI())


def LLS():
    return [list(map(str, l.split())) for l in eval(input())]


def LLI():
    return [list(map(int, l.split())) for l in eval(input())]


def LLSN(n: int):
    return [LS() for _ in range(n)]


def LLIN(n: int):
    return [LI() for _ in range(n)]


A, B, C, D = MI()
t = A
a = C
for i in range(100):
    a -= B
    if a <= 0:
        print("Yes")
        exit()
    t -= D
    if t <= 0:
        print("No")
        exit()

from math import floor, ceil, sqrt, factorial, log
from collections import Counter, deque
from functools import reduce

# import numpy as np
def S():
    return eval(input())


def I():
    return int(eval(input()))


def MS():
    return list(map(str, input().split()))


def MI():
    return list(map(int, input().split()))


def FLI():
    return [int(i) for i in input().split()]


def LS():
    return list(MS())


def LI():
    return list(MI())


def LLS():
    return [list(map(str, l.split())) for l in eval(input())]


def LLI():
    return [list(map(int, l.split())) for l in eval(input())]


def LLSN(n: int):
    return [LS() for _ in range(n)]


def LLIN(n: int):
    return [LI() for _ in range(n)]


A, B, C, D = MI()
x = -(-A // D)
y = -(-C // B)
if x >= y:
    print("Yes")
else:
    print("No")
# for i in range(100):
#     a -= B
#     if a <= 0:
#         print("Yes")
#         exit()
#     t -= D
#     if t <= 0:
#         print("No")
#         exit()

-import numpy as np - +# import numpy as np -t = A -a = C -for i in range(100): -    a -= B -    if a <= 0: -        print("Yes") -        exit() -    t -= D -    if t <= 0: -        print("No") -        exit() +x = -(-A // D) +y = -(-C // B) +if x >= y: +    print("Yes") +else: +    print("No") +# for i in range(100): +#     a -= B +#     if a <= 0: +#         print("Yes") +#         exit() +#     t -= D +#     if t <= 0: +#         print("No") +#         exit()