#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)
	{
		c/= 1200.0;
		++c;
		double dpt = X;
		//Y*= 1;

		for(int i=1; i<=N;i++)
		{
			dpt = dpt*pow(c,12.0) - Y * ( (pow(c,12) - 1) / (c-1)  );
			if (dpt < 0)
				break;
		}
		if (dpt < 0)
			puts("YES");
		else
			puts("NO");
	}
	
	return 0;
}