Program P114;
 { Efecte colaterale }
var a, b : real;

procedure P(var x, y : real);
 { Interschimbarea valorilor variabilelor x, y }
begin
 a:=x;
 x:=y;
 y:=a;
end; { P }

begin
 a:=1; b:=2;
 P(a, b);
 writeln(a, b);
 a:=3; b:=4;
 P(a, b);
 writeln(a, b);
 readln;
end.