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

using namespace std;

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

	while(cin>>X>>Y>>N>>c,N>0.5)
			//scanf("%lf %lf %lf %lf", &X, &Y, &N, &c),N>0.5)
	{
		c/= 1200.0;
		c+= 1.0;

		long double k = pow(c,N*12.0);
		long double dpt = X*k - Y * ( (k-1.0) / (c-1.0)  );
		
		//printf("%lf\n",(double)dpt);
		if (dpt <= 1e-8)
			printf("YES\n");
		else
			printf("NO\n");
	}
	
	return 0;
}