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

L_mod = L % M
R_mod = R % M

if K == 0:
    print("Yes")
else:
    if L_mod > R_mod:
        print("Yes")
    elif L_mod == 0:
        print("Yes")
    else:
        if R_mod * K >= M:
            print("Yes")
        else:
            print("No")