uses crt;
var i,n,s:longint;
begin
clrscr;
readln(n);
s:=1;
for i:=1 to n do
if i mod 2=0 then s:=s*i;
writeln(s);
readln;
end.
Var i,t:integer;
Begin
Write('Nhap n = ');readln(n);
t:=1;
For i:=1 to n do
If i mod 2 = 0 then t:=t*i;
Write('t = ',t);
Rradln;
End.