Program CTC_2;
uses crt;
var n:integer;
x:longint;
Procedure Giai_Thua
(var GT:longint; n:byte);
begin GT:=1;
while n>0 do begin GT:=GT*n;
n:=n-1;
end;
end;
begin repeat clrscr;
write('Nhap so n: ');readln(n);
if n < 0 then begin write('Nhap so n>=0');readln;
end;
until n>=0; Giai_Thua(x,n);
writeln('Giai thua cua ',n,'la:',x);
readln
end.