L, R, M, K = map(int, input().split())

if(K == 0):
    print("Yes")
    exit()

diff = (R * K) - (L * K)

mod_diff = M - ((L * K) % M)
if mod_diff == M:
    mod_diff = 0

if diff >= mod_diff:
    print("Yes")
else:
    print("No")