uses crt;
var x1,x2,y1,y2,a,z,d1,d2:real;
begin
clrscr;
write('vvedite a: ');
readln(a);
d1:=1-4*2*(-4);
x1:=(-1-sqrt(d1))/2*2;
x2:=(-1+sqrt(d2))/2*2;
d2:=sqr(2)-4*a*(-1);
y1:=(-2-sqrt(d2))/2*a;
y2:=(-2+sqrt(d2))/2*a;
z:=(x1+y1)/(x2+y2);
writeln('z=',z:3:2);
end.