import sys
input = sys.stdin.readline

# from collections import deque

def linput(_t=int):
    return list(map(_t, input().split()))

def say(n):
    print(("No","Yes")[n%2])
    exit(0)

def gcd(n,m):
    while m: n,m = m, n%m
    return n

def lcm(n,m): return n*m//gcd(n,m)

def main():
    # N = int(input())
    # N,K = linput()
    L,R,M,K = linput()
    # vA = linput()
    # vE = [linput() for _ in [0,]*M]

    res = 0

    if K*L==0:
        say(1)

    if M==1:
        say(1)

    if (R-L)*K >= M:
        say(1)

    if L==R:
        if K*L%M != 0:
            say(0)
        else:
            say(1)

    if K*L%M > K*R%M:
        res = 1

    # print(res)
    say(res)


main()