I have changed a lot: readln to read, integer to longint, double to
erxtended. But get WA!

Please, tell me - what's wrong here. I want not to send accepted
program which is on the message board, but to understand my error.
Can I use any variable on Timus - like a, a0? Does sqrt work on Timus?
Does Pascal has constant PI?

Thanks for any help.

program p1020;
var
  i,n:longint;
  r,res,a0,b0,a1,b1,a2,b2:extended;
begin
  read(n,r);
  read(a1,b1);
  res := 2*PI*r; a0 := a1; b0:=b1;
  for i:=1 to n-1 do
  begin
    read(a2,b2);
    res := res + sqrt((a2-a1)*(a2-a1)+(b2-b1)*(b2-b1));
    a1 := a2; b1:=b2;
  end;
  res := res + sqrt((a2-a0)*(a2-a0)+(b2-b0)*(b2-b0));
  writeln(res:0:2);
end.