

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

#print( a, b, c, d )

 

for i in range( 200 ):

    c = c - b

    if c <= 0:

        print( "Yes" )

        exit()

 

    a = a - d

    if a <= 0:

        print( "No" )

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

#print( a, b, c, d )

 

for i in range( 200 ):

    c = c - b

    if c <= 0:

        print( "Yes" )

        break

 

    a = a - d

    if a <= 0:

        print( "No" )

        break
a, b, c, d = list(map(int, input().split()))
# print( a, b, c, d )
for i in range(200):
    c = c - b
    if c <= 0:
        print("Yes")
        exit()
    a = a - d
    if a <= 0:
        print("No")
        exit()

a, b, c, d = list(map(int, input().split()))
# print( a, b, c, d )
for i in range(200):
    c = c - b
    if c <= 0:
        print("Yes")
        break
    a = a - d
    if a <= 0:
        print("No")
        break

-        exit() +        break -        exit() +        break