Вычислить y=1!-3!+5!-..+(-1)^(n-1)(2n-1)! — Pascal(Паскаль)

Uses
 CRT;
Var
 i,n,l,j:integer;
 f,sum:real;
begin
readln(n);
l:=1;
sum:=0;
i:=1;
repeat
begin
 f:=1;
 j:=1;
  repeat
   f:=f*(j);
   inc(j);
  until j>i*2-1;
 sum:=sum+(l*f);
 l:=-l;
inc(i);
end;
until i>n;
write(sum);
end.

Uses
 CRT;
Var
 i,n,l,j:integer;
 f,sum:real;
begin
readln(n);
l:=1;
sum:=0;
for i:=1 to n do
begin
f:=1;
for j:=1 to i*2-1 do
f:=f*(j);
sum:=sum+(l*f);
l:=-l;
end;
write(sum);
end.