Вычислить факториал числа N (N!). (прим: 5!=1*2*3*4*5)

Const len = 1000;

type

longnum = array[1 ... len] of longint;

var

n, i: longint;

s: longnum;

procedure InitLongNumber (n: longint; var a: longnum) ;

var

i: longint;

begin

for i : = 1 to len do

if n 0 then

begin

a[i] : = n mod 10;

n : = n div 10

end else

a[i] : = 0;

end;

function mul (a: longnum; k: longint) : longnum;

var

i, tmp: longint;

begin

tmp : = 0;

for i : = 1 to len - 1 do

begin

a[i] : = a[i] * k + tmp;

tmp : = a[i] div 10;

a[i] : = a[i] mod 10

end;

result : = a

end;

procedure PrintLongNumber (a: longnum) ;

var

i, j: longint;

begin

i : = len;

while a[i] = 0 do

dec (i) ;

for j : = i downto 1 do

write (a[j])

end;

begin

readln (n) ;

InitLongNumber (1, s) ;

for i : = 1 to n do

s : = mul (s, i) ;

write (n, '! = ') ;

PrintLongNumber (s) ;

end.