Adding max elements from each row in 2D vector such that row element a_I is less that a_(i+1)

#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
int main()
{
int t,n,v1;
vector < vector<int> > vec;
vector<int> max;
cin>>t;
while(t--)
{
 cin>>n;
 for(int i=0; i<n; i++)
 {  vector<int> row;
    for(int j=0; j<n; j++)
    {
     int val;
      cin>>val;
      row.push_back(val);   
     }
     vec.push_back(row);
       }    

for (int i=0; i<n; i++)
{
    for(int j=0; j<n; j++)
    {
        v1=*max_element(vec.begin(), vec.end());
        max.push_back(v1);
    }
}

if(is_sorted(max.begin(),max.end()))
{
    cout<<accumulate(max.begin(), max.end(),0)<<endl;

}

else
cout<<"-1"<<endl;

}
return 0;
 }