program Background;

var

a,b:array[1..100] of real;

n,i:integer;

r,s,c,l:real;

begin

read(n,r);

for i:=1 to n do read(a[i],b[i]);

for i:=1 to n-1 do

begin

c:=sqr(a[i]-a)+sqr(b[i]+b);

l:=sqrt(c)+l;

c:=0;

end;

s:=3.1415926*sqr(r)+sqrt(sqr(a[1]-a[n])+sqr(b[1]+b[n]));

write(l+s:4);

end.

如何修改才能通过?