Viết CT tính S=1.3.5...(2n-1)

program giai;

uses crt;

var n,i,s:longint;

begin

readln(n);

S:=1;

for i:=1 to 2*n-1 do

if i mod 20 then S:=S*i;

writeln(S);

readln;

end.