long sfold(String s, int M) {
  int intLength = s.length() / 4;
  long sum = 0;
  for (int j = 0; j < intLength; j++) {
    char c[] = s.substring(j * 4, (j * 4) + 4).toCharArray();
    long mult = 1;
    for (int k = 0; k < c.length; k++) {
      sum += c[k] * mult;
      mult *= 256;
    }
  }

  char c[] = s.substring(intLength * 4).toCharArray();
  long mult = 1;
  for (int k = 0; k < c.length; k++) {
    sum += c[k] * mult;
    mult *= 256;
  }

  sum = (sum * sum) >> 8;
  return(Math.abs(sum) % M);
}