Вычислить сумму факториалов четных чисел от M до N

var m, n, f, s, i: longint;
 
begin
    readln(m, n);
    f := 1;
    s := 0;
    for i := 2 to n do begin
        f *= i;
        if (i >= m) and (i mod 2 = 0) then begin
            s += f;
        end;
    end;
    writeln(s);
end.

type Num = longint;
 
type Fac = record
    f: Num;
    i: Num;
end;
 
type PFac = ^Fac;
 
procedure Fac_init(self: PFac);
begin
    self^.f := 1;
    self^.i := 0;
end;
 
function Fac_get(self: PFac; n: Num): Num;
begin
    while self^.i < n do begin
        inc(self^.i);
        self^.f *= self^.i;
    end;
    Fac_get := self^.f;
end;
 
var m, n, s: Num;
var f: Fac;
 
begin
    readln(m, n);
    s := 0;
    Fac_init(addr(f));
    m := ((m + 1) shr 1) shl 1;
    while m <= n do begin
        s += Fac_get(addr(f), m);
        m += 2;
    end;
    writeln(s);
end.

    for i := 2 to m-1 do f *= i;
    for i := m to n and not 1 do begin
        f *= i;
        if not Odd(i) then s += f;
    end;

type
  Num = longint;
  PFac = ^Fac;
  Fac = record
    f: Num;
    i: Num;
  end;
 
procedure Fac_init(var self: Fac);
begin with self do begin
    f := 1;
    i := 0;
end end;
 
function Fac_get(var self: Fac; n: Num): Num;
begin with self do begin
    while i < n do begin
        inc(i);
        f *= i;
    end;
    Fac_get := f;
end;
var
  m, n, s: Num;
  f: Fac;
begin
    readln(m, n);
    s := 0;
    Fac_init(f);
    m := (m + 1) and not 1;
    while m <= n do begin
        s += Fac_get(f, m);
        m += 2;
    end;
    writeln(s);
end.

function fact(n: Integer): Longint;
const
  LastN: Integer = 0;
  LastF: LongInt = 1;
begin
  if n < LastN then begin
    LastN := 0;
    LastF := 1;
  end;
  while LastN < n do begin
    Inc(LastN);
    LastF := LastF * LastN;
  end;
  fact := LastF;
end;

var
  m, n: Integer;
  s: LongInt;
begin
  ReadLn(m, n);
  m := (m + 1) and not 1;
  n := n and not 1;
  while m <= n do begin
    s += fact(m);
    Inc(m, 2);
  end;
  WriteLn(s);
end.