#include <cstdio>
#include <vector>
using namespace std;

int main(){
	using std::vector;
	int H, W, N, K;
	int i;
	int size;
	fscanf(stdin, "%d %d %d %d", &H, &W, &N, &K);
	size = H * W;
	if (size > N) {
		size = size % N;
	}
	//vector<vector<int>> arr(H, vector<int>(W));
	if (size == K) {
		printf("YES\n");
	}
	else {
		printf("NO\n");
	}
	return 0;
}