var a,b,t,x,y:real;
begin
t:=-5;
a:=8.2;
b:=-0.3;
 
while (t<=22) do begin
x:=3*t+t;
if (x<15) then y:=(a+b)/x 
else if (x>=25) then y:=(a+b)/(x+1) 
else y:=a+ln(x);
t:=t+3;
writeln ('y','=',y);
end;

end.