var S,rm,R:real;
begin
write('vnutrennii radius=');
readln(rm);
write('vneshnii radius=');
readln(R);
If R>rm then
begin
S:=3.14*(sqr(R)-sqr(rm));
Writeln('ploschad kolca = ',S);
end
else
Writeln('vvedeny nepravilnye dannye');
end.