program p1;
var a,b:integer;
function factorial(n:integer):longint;
begin
if n < 0 then factorial:=-1 else
if n < 2 then factorial:=1 else
factorial:=n * factorial(n-1);end;
begin
write('a=');
readln(a);
write('b=');
readln(b);
writeln(factorial(a)*factorial(b));
readln;
end.
