自己看

Const

pi=3.1415926;

Var

mark1,mark2,r,sn,re1,re2,data1,data2:real;

n,i:integer;

Begin

readln(n,r);

if n=1 then writeln(r*pi*2:0:2);

if n>1 then

begin

readln(re1,re2);

mark1:=re1;mark2:=re2;

for i:=1 to n do

begin

if i