program
figuri;
var
R1,R2,a,b:
real;
begin
writeln('vvedite
radius R1 opisannoi okrujnosti');
readln(R1);
writeln('vvedite
storonu a priamougolnika');
readln(a);
b:=sqrt(
(4*sqr(R1)) - sqr(a));
R2:=b/2;
writeln('radius
R2 vpisannogo kruga =',R2);
end.