bai 13
var x, y, z:longint;
P:real;
bai 14
var a:qword;
begin
writeln('nhap so nguyen a');
readln(a);
if a mod 9=0 then writeln('so nay chia het cho 9 va 3')
else if a mod 3=0 then writeln('so nay chi chia het cho 3')
else writeln('so nay khong chia het cho 3 va 9');
readln;
end.
bai 15
var a,b,c:qword;
s:real;
begin
writeln('nhap lan luot 3 so a, b, c');
readln(a,b,c);
if (a+b>c)and(a+c>b)and(b+c>a) then begin
s:=(a+b+c)/2;
s:=sqrt(p*(p-a)*(p-b)*(p-c));
writeln('day la 3 canh tam giac co chu vi la :',s);
end else write('day khong phai 3 canh cua tam giac');
readln;
end.
