# import sys; input = sys.stdin.buffer.readline
# sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")
import copy

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

#処理内容
def main():
	H, W, N, K = getlist()
	if (H + W - 1) % N == K % N:
		print("YES")
	else:
		print("NO")

if __name__ == '__main__':
	main()