program hoanvi;
var a,b,x:integer;
begin
writeln('nhap so a');readln(a);
writeln('nhap so b'); readln(b);
x:=a;
a:=b;
b:=x;
writeln('hai so a b sau khi hoan vi' ,a,b:4);
readln;
end.
{ dung chuong trinh con}
program chuongtrinh;
var a,b,x:integer;
begin
procedure hoanvi;
begin
writeln('nhap so a'); readln(a);
writeln('nhap so b'); readln(b);
x:=a;
a:=b;
b:=x;
writeln('so sau khi hoan vi , 'a ,b:4);
end;
begin
hoanvi;
end.