var
  a: array[1..100] of byte;
  n, i: byte;
  pr: int64;

begin
  pr := 1;
  readln(n);
  for i := 1 to n do
    read(a[i]);
  for i := 1 to n do
    if (i mod 2 = 1) then pr *= a[i]; // pr:=pr*a[i];
  writeln(pr);
end.