program sum;
{$APPTYPE CONSOLE}
uses SysUtils;
var teihen: real;
var takasa: real;
var menseki: real;
begin
    write('Please Enter teihen: ');
    readln(teihen);
    write('Please Enter takasa: ');
    readln(takasa);
    menseki := teihen*takasa*0.5;
    writeln('menseki =', menseki:8:3);
    readln
end.