Sorting of 2D vector in C++

#include <bits/stdc++.h>
using namespace std;

bool comp(vector<int> &a, vector < int > &b )
{
return a[1]<b[1] ;
}

int main()
{
vector<vector<int>> v = {{2,3}, {4,7} , {3,5} , {7,9}, {1,4}};
sort(v.begin(), v.end(),comp) ;
for ( int i = 0 ; i < v.size() ; i ++ )
cout<<v[i][0]<<" " <<v[i][1]<< " " <<endl;
return 0;
}