def main with input n output result as
  if (n % 2) == 0 then result := 1
  else (
    result := 0;
    s := 0;
    while (0 == ((n - 1) / (2 ^ s)) % 2) do (
      s := s + 1
    );
    d := ((n - 1) / 2 ^ s);
    for (i := 20, i > 0, i := i - 1) do (
      a := rand(n - 4) + 2;
      x := powmod(a, d, n);
      y := 0;
      for (j := 0, j < s, j := j+1) do (
        y := powmod(x, 2, n);
        if (y == 1 && (not x == 1) && (not x == n - 1)) then
          result := 1;
        else
          skip;
        x := y;
      );
      if not y == 1 then result := 1;
                    else skip;
    )
  )