I am getting WA for subtasks 8,9 and 11. Unable to figure out the problem. Here is my code.

#include<bits/stdc++.h>
#define loop(n) for( i=0;i<n;i++)
using namespace std;
vector <int> v1,v2;
int n,k,a,temp,i,s1,s2;
void keep_()
{
  sort(v1.begin(),v1.end(),greater<int>());
  sort(v2.begin(),v2.end(),greater<int>());
if(v1.front()>v2.front())
{
      sort(v1.begin(),v1.end());
      loop(n)
{
if(v1[i]>v2[i]|| i==k)break;
}
      s1=v1[n-1]+v2[i];
      sort(v1.begin(),v1.end(),greater<int>());
      temp=v1[0];
      v1[0]=v2[n-1];