J problema

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;


int
sumanPrimos (int a, int b)
{
  vector < int >primos = { 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31 };


  int suma = a + b;

// When the element is not found, std::find returns the end of the range
  if (find (primos.begin (), primos.end (), suma) != primos.end ())
    {
      return 1;
    }
  else
    {
      return 0;
    }
}

int
printVector (vector < int >&vec)
{
  for (int i = 0; i < vec.size (); i++)
    {

      cout << vec[i] << " ";
    }

    cout <<endl;
    return 0;
}

int
backtracking (vector < int >&acum, int max, int last)
{

  if (acum.size () == max)
    {
        if( sumanPrimos (last, acum[0])){

            printVector (acum);

        }
        return 0;
    }
  else
    {
      for (int i = 2; i <= max; i++)
    {
//si no lo he usado aun
      if (find (acum.begin (), acum.end (), i) == acum.end ())
        {
          if (sumanPrimos (i, last))
        {
          vector < int >acum1 = acum;
          acum1.push_back (i);
          backtracking (acum1, max, i);
        }
        }
    }
      return 0;
    }
}

int
main ()
{
  int n;
  int cnt = 1;
  while(cin >> n){
    cout << "Case " << cnt << ":" << endl;
    cnt++;
    for (int i = 2; i <= n; i++)
        {
        if (sumanPrimos (1, i)){

            vector < int >acum = { 1, i };
            backtracking (acum, n, i);
        }
    }
    cout<< endl;

  }
  return 0;
}