Yes! I found why my submition gives WA - but can't understand why.

Here is my WA solution:

program p1020;
var
  i,n:integer;
  r,res,a0,b0,a1,b1,a2,b2:double;
begin
  read(n,r);
  read(a1,b1);
  res:=0.0; a0 := a1; b0:=b1;
  for i:=1 to n-1 do
  begin
    readln(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));
  res := res + 2*PI*r;
  writeln(res:0:2);
end.

!!!! BUT when I  change a line
    res := res + sqrt((a2-a0)*(a2-a0)+(b2-b0)*(b2-b0));
to
    res := res + sqrt((a1-a0)*(a1-a0)+(b1-b0)*(b1-b0));
I get ACCEPTED!!!

Tell me smb, WHY?????

Try this input:

1 1
2 2

Output should be 6.28, but your first program outputs 9.11

> Try this input:
>
> 1 1
> 2 2
>
> Output should be 6.28, but your first program outputs 9.11