var   x1,x2,h,v,s1,l,k:real; 
i,f1,f2,n:longint; 
begin 
assign(input,'freefaller.in');assign(output,'freefaller.out');reset(input);rewrite(output);
read(input,h,s1,v,l,k,n);
X1:=s1-V*sqrt((2*(h-k))/10)+0.00001;f1:=n-1;f2:=n-1;
for i:=0 to n-1 do		 if (x1+l)<i then		    
	begin			
f1:=i;		  
break; 
end;
x2:=s1-V*sqrt((2*h)/10)-0.00001;
for i:=0 to f1 do			 
	if x2<i then
		begin
f2:=i;				 break;
end;	 if (x1>n-1)and(x2<n-1) then dec(f2);      writeln(output,f1-f2); close(input);close(output);	  end.