// better modulo that gives positive numbers always
static int mod(int n, int m) {
  ret (n % m + m) % m;
}

static long mod(long n, long m) {
  ret (n % m + m) % m;
}

static BigInt mod(BigInt n, int m) {
  ret n.mod(bigint(m));
}

static double mod(double n, double m) {
  ret (n % m + m) % m;
}