#include <stdio.h>
#include <time.h>

void check(int *a, int *b);

int main(void){
	int h, w, n, k, count = 1;

	scanf("%d %d %d %d", &h, &w, &n, &k);

	if (h > w) {
		h = h - w;
		w = 1;
	}
	else if(h < w) {
		w = w - h;
		h = 1;
	}
	else{
		h = 1;
		w = 1;
	}

	n = n - k;
	k = 1;

	for(;;){
		if(w == 1 && h == 1){
			if(count == k)
				printf("YES\n");
			else
				printf("NO\n");
			break;
		}
		if(h > w) check(&h, &w);
		else	  check(&w, &h);
		
		count++;
		if(count == n + 1)
			count = 1;
	}

	return 0;
}

void check(int *a, int *b){
	if(*a == 0){
		if(*b != 0)
			(*b)--;
	}
	else
		(*a)--;
}