Language: C++

#include<bits/stdc++.h>
using Namespace std;
#define int long long
typedef pair<int ,int> P;
int N,K;
signed main(){
  cin >> N >> K;
  int mx=(N-1)*(N-2)/2;
  if(mx<K){
    puts("-1");
    return 0;
  }
  vector<P> ans;
  for(int i=0;i<N-1;i++){
    ans.push_back(P(i+1,N));
  }
  int add=mx-k;
  vector<P> edge;
  for(int i=0;i<N-1;i++){
    for(int j=0;j<i;j++){
      edge.push_back(P(i+1,j+1));
    }
  }
  for(int i=0;i<add;i++) ans.push_back(edge[i]);
  cout << ans.size() << endl;
  for(int i=0;i<ans.size();i++){
    cout << ans[i].first << " " << ans[i].second << endl;
  }
  return 0;
}


Compiler output:
a.cc:2:7: error: expected nested-name-specifier before 'Namespace'
    2 | using Namespace std;
      |       ^~~~~~~~~
a.cc:4:9: error: 'pair' does not name a type
    4 | typedef pair<int ,int> P;
      |         ^~~~
a.cc: In function 'int main()':
a.cc:7:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    7 |   cin >> N >> K;
      |   ^~~
      |   std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146,
                 from a.cc:1:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:13:3: error: 'vector' was not declared in this scope
   13 |   vector<P> ans;
      |   ^~~~~~
a.cc:13:3: note: suggested alternatives:
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53:
/usr/include/c++/14/bits/stl_vector.h:428:11: note:   'std::vector'
  428 |     class vector : protected _Vector_base<_Tp, _Alloc>
      |           ^~~~~~
/usr/include/c++/14/vector:93:13: note:   'std::pmr::vector'
   93 |       using vector = std::vector<_Tp, polymorphic_allocator<_Tp>>;
      |             ^~~~~~
a.cc:13:10: error: 'P' was not declared in this scope
   13 |   vector<P> ans;
      |          ^
a.cc:13:13: error: 'ans' was not declared in this scope; did you mean 'abs'?
   13 |   vector<P> ans;
      |             ^~~
      |             abs
a.cc:17:14: error: 'k' was not declared in this scope
   17 |   int add=mx-k;
      |              ^
a.cc:18:13: error: 'edge' was not declared in this scope
   18 |   vector<P> edge;
      |             ^~~~
a.cc:25:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   25 |   cout << ans.size() << endl;
      |   ^~~~
      |   std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:25:25: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   25 |   cout << ans.size() << endl;
      |                         ^~~~
      |                         std::endl
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~