char* convert(const char* str) {
  char* end = str + strlen(str) - 1;
  char* result = malloc(sizeof(str));
  size_t result_id = 0;
  size_t current_symbol = 0;
  size_t pow_2 = 1;
  while (end >= str) {
    if (*end == '1') {
      current_symbol += pow_2;
    }

    if (pow_2 == 8 || end == str) {
      pow_2 = 1;
      if (current_symbol <= 9) {
        result[result_id++] = '0' + current_symbol;
      } else {
        result[result_id++] = 'A' + current_symbol - 10;
      }
      current_symbol = 0;
    } else {
      pow_2 *= 2;
    }

    --end;
  }
  result[result_id--] = '\0';
  for (size_t i = 0; i < result_id; ++i) {
    if (i < result_id - i) {
      char tmp = result[i];
      result[i] = result[result_id - i];
      result[result_id - i] = tmp;
    } else {
      break;
    }
  }

  return result;

}