#include<stdio.h>
#include<math.h>


int main()
{
	int X, Y, N;
	double c;

	while(scanf("%d %d %d %lf", &X, &Y, &N, &c),N>0)
	{
		c/= 1200.0;
		++c;

		double k = pow(c,N*12);
		double dpt = X*k - Y * ( (k-1) / (c-1)  );
		
		if (dpt < 0)
			printf("YES\n");
		else
			printf("NO\n");
	}
	
	return 0;
}