uses crt;
var l,r,s:real;
begin
clrscr;
write('L -> ');
readln(l);
r := l/2/pi;
s := pi * sqr(r);
writeln('S=',s:0:4);
readln;
end.
uses crt;
var l,r,s:real;
begin
clrscr;
write('L -> ');
readln(l);
r := l/2/pi;
s := pi * sqr(r);
writeln('S=',s:0:4);
readln;
end.