#include <stdio.h>
#include <math.h>
#include <string.h>

#define BIG_SIZE (400000)
void test(int actual, int expected);

// NOTE: since N is not given, we assume standard string termination (\0)

int solution(char* str) 
{
  int sum = 0;
  while (str[0] == '0'         // skip leading zeros
         && str[0] != '\n') {  // handle zero-only strings
    ++str;
  }
  while (str[0] != '\0') {
    if (str[0] == '0') {
      sum += 1;
    }
    else {
      sum += 2;
    }
    ++str;
  }
  return sum ? sum -1 : 0; 
}

int main()
{
  test(solution("0"), 0);
  test(solution("00000"), 0);
  test(solution("1"), 1);
  test(solution("011100"), 7);
  test(solution("111"), 5);
  test(solution("1111010101111"), 22);
  
  char str[BIG_SIZE+1];
  memset(str, '1', BIG_SIZE+1);
  str[BIG_SIZE] = '\0';
  test(solution(str), 799999);

  printf("Done\n");
}

// -----

void test(int actual, int expected)
{
  if (actual != expected) {
    printf("Test failed, expected %i, got %i\n", expected, actual);
  }
  else {
    printf("Test passed (expected %i, got %i)\n", expected, actual);
  }
}

// alternative solution:
// int solution(char* str)
// {
//   int sum = 0;
//   int i = 0;
//   while (str[i] == '0' && str[i] != '\n') {
//     ++i;
//   }

//   while (str[i] != '\0') {
//     if (str[i] == '0') {
//       sum += 1;
//     }
//     else {
//       sum += 2;
//     }
//     ++i;
//   }
//   return sum ? sum -1 : 0; 
// }