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

using namespace std;

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

	while(true)
	{
		scanf("%lf %lf %lf %lf", &X, &Y, &N, &c);
		if (N < 1)
			return 0;
		
		c/= 1200.0;
		c+= 1.0;

		long double dpt = X, k;
		for(int i=1; i<=N; i++)
		{
			k = pow(c,12.0);
			dpt = k*dpt - Y * ( (k-1.0) / (c-1.0)  );		
		}
		
		//printf("%lf\n",(double)dpt);
		if ( dpt < 0 )
			printf("YES\n");
		else
			printf("NO\n");
	}
	
	return 0;
}