uses crt;

var i,n,s: integer;

begin

clrscr;

write ('nhap n: ');  readln (n);

s:=1;

for i:=1 to n do if i mod 2=1 then s:=s*i;

writeln ('tich la: ',s);

readln;

end.

- Sử dụng for .. to .. do :

uses crt;

var i, n, T : longint;

begin

clrscr;

write('Nhap so n = '); readln(n);

T := 1;

for i := 1 to n do

if i mod 2 <> 0 then T := T * i;

write('T = ', T);

readln

end.

- Sử dụng while .. do

uses crt;

var i, n, T : longint;

begin

clrscr;

write('Nhap so n = '); readln(n);

T := 1; i := 1;

while i <= n do begin

if i mod 2 <> 0 then T := T * i;

i := i + 1; end;

write('T = ', T);

readln

end.