#include <stdio.h>

int main() {
	long long int h, w, n, k;
	scanf("%lld%lld%lld%lld", &h, &w, &n, &k);
	
	h--; w--; k--;
	printf("%s\n", (h + w) % n == k ? "YES" : "NO");
	
	return 0;
}