a, #include <bits/stdc++.h>
using namespace std;
int main()
{
 int r;
 cin>>r;
 cout<<"Chu vi hinh tron "<<r*2*3.14<<endl;
 cout<<"Dien tich hinh tron "<<r*r*3.14<<endl;
 cout<<"The tich hinh tron "<<r*r*r*3.14*4/3;
}

b, #include <bits/stdc++.h>
using namespace std;
int main()
{
 int r;
 cin>>r;
 if(r<0) cout<<"Sai du lieu";
 else
 {
 cout<<"Chu vi hinh tron "<<r*2*3.14<<endl;
 cout<<"Dien tich hinh tron "<<r*r*3.14<<endl;
 cout<<"The tich hinh tron "<<r*r*r*3.14*4/3;
 }
}

`#AC`

uses crt;
var r:longint;
begin
clrscr;
   write('a) Nhap ban kinh: ');readln(r);
   if r<=0 then writeln('b) Ban kinh khong hop le') else
      begin
         writeln('b) Ban kinh hop le');
         writeln('Chu vi hinh tron: ',2*r*pi:0:3);
         writeln('Dien tich hinh tron: ',r*r*pi:0:3);
         writeln('The tich hinh cau: ',4*pi*r*r*r/3:0:3);
      end;
readln
end.