#include <iostream>
#include <string>

/*  algorithm that "hashes" the through digit sum. The size needed for
 * this would be 64, since telephone numbers are exactly 7 digits long and the
 * maximum value a digit can have is 9 -> 7*9 = 63, plus 1 since we start at
 * zero. */
int digitSum(std::string telNr) {
  uint32_t number = std::stoi(telNr);
  uint8_t digitSum = 0;
  while (number > 0) {
    digitSum += number % 10;
    number /= 10;
  }
  return digitSum;
}

int main() { std::cout << digitSum("9797979") << std::endl; }