uses crt;
procedure area(r:real; var s:real);
begin
s:=4*Pi*sqr(r);
end;
var r1,r2,s1,s2:real;
begin
clrscr
repeat
write('r1,r2: (r1>r2):');
readln(r1,r2);
until r1>r2;
area(r1,s1);
area(r1,s2);
write(s1-s2);
readln
end.
uses crt;
procedure area(r:real; var s:real);
begin
s:=4*Pi*sqr(r);
end;
var r1,r2,s1,s2:real;
begin
clrscr
repeat
write('r1,r2: (r1>r2):');
readln(r1,r2);
until r1>r2;
area(r1,s1);
area(r1,s2);
write(s1-s2);
readln
end.