Codechef Discrepancies in the Voters List Problem Code: VOTERS

#include <iostream>
#include <vector>

using namespace std;
int main(){
  int n1,n2,n3;
  cin>>n1>>n2>>n3;
  vector<int> a(1e8+4);
  int n=0;
  while((n1&&n1--)||(n2&&n2--)||(n3&&n3--)){
    int tmp;
    cin>>tmp;
    if(++a[tmp]==2)
      n++;
  }
  cout<<n<<endl;
  for(int i=0;i<1e8+2;i++)
    if(a[i]>1)
      cout<<i<<endl;
}