Var
 i:Byte;

Procedure Triangular;
var base,height:real;
begin
 write('Base side: ');
 readln(base);
 write('Height: ');
 readln(height);
 writeln('Square = ',base*height/2:0:3);
end;

Procedure Square;
var side:real;
begin
 write('Side: ');
 readln(side);
 writeln('Square = ',Sqr(side):0:3);
end;

Procedure Rectangle;
var side1,side2:real;
begin
 write('First side: ');
 readln(side1);
 write('Second side: ');
 readln(side2);
 writeln('Square = ',side1*side2:0:3);
end;

Procedure Trapezium;
var base1,base2,height:real;
begin
 write('Long base: ');
 readln(base1);
 write('Short base: ');
 readln(base2);
 write('Height: ');
 readln(height);
 writeln('Square = ',(base1+base2)*height/2:0:3);
end;

Procedure Circle;
var radius:real;
begin
 write('Radius: ');
 readln(radius);
 writeln('Square = ',Pi*Sqr(radius):0:3);
end;

Procedure Ring;
var Big_r,Small_r:real;
begin
 write('Big radius: ');
 readln(Big_r);
 write('Small radius: ');
 readln(Small_r);
 writeln('Square = ',Pi*(Sqr(Big_r)-Sqr(Small_r)):0:3);
end;

Begin
 Repeat
  Writeln('Choose a figure:');
  Writeln('                1 - Triangular');
  Writeln('                2 - Square');
  Writeln('                3 - Rectangle');
  Writeln('                4 - Trapezium');
  Writeln('                5 - Circle');
  Writeln('                6 - Ring');
  Writeln('                7 - Exit');
  Readln(i);
  Case i of
   1: Triangular;
   2: Square;
   3: Rectangle;
   4: Trapezium;
   5: Circle;
   6: Ring;
  End;
 Until i=7;
End.