Language: C++

#include <iostream>
#include <iomanip>
#include <cmath>
#include <string>
#include <vector>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <queue>
#include <numeric>
#include <random>
#include <algorithm>
#include <functional>
#include <cassert>

using namespace std;
typedef long long ll;

template<class T> inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template<class T> inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

const int INF = (1 << 30) - 1;
const ll INFLL= (1LL << 61) - 1;
const int MOD = 1000000007;
#define ALL(a) (a).begin(),(a).end()
#define rALL(a) (a).rbegin(),(a).rend()
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)

struct r2{int x,y;};
vector<r2> ans;

void move(int x,int y){
  nowx+=x;nowy+=y;
  ans.push_back({nowx,nowy});
}

int main(){
  cin>>k>>x>>y;

  if(!(k&1)&&((x+y)&1)){
    cout<<-1<<endl;
    return 0;
  }
  if(abs(x)+abs(y)==k){
    cout<<1<<endl<<x<<" "<<y<<endl;
    return 0;
  }

  int X=abs(x),Y=abs(y);
  if(X>Y)swap(X,Y);

  int sousai=-1;
  for(int j=k*2;sousai<0;j+=k)
    if((j-(X+Y))%2==0)sousai=(j-(X+Y))/2;

  if(sousai){
    while(sousai>=k){
      move(0,-k);
      sousai-=k;
    }
    move(-sousai,k-sousai);
  }

  while(nowx+k<=X)move(k,0);
  while(nowy+k<=Y)move(0,k);
  if(nowx!=X||nowy!=Y)ans.push_back({X,Y});

  cout<<ans.size()<<endl;

  for(auto p:ans){
    int ansx=p.x,ansy=p.y;
    if(abs(x)>abs(y))swap(ansx,ansy);
    if(x<0)ansx*=-1;
    if(y<0)ansy*=-1;
    cout<<ansx<<" "<<ansy<<endl;
  }
}


Compiler output:
a.cc: In function 'void move(int, int)':
a.cc:47:3: error: 'nowx' was not declared in this scope
   47 |   nowx+=x;nowy+=y;
      |   ^~~~
a.cc:47:11: error: 'nowy' was not declared in this scope
   47 |   nowx+=x;nowy+=y;
      |           ^~~~
a.cc:48:16: error: no matching function for call to 'std::vector<r2>::push_back(<brace-enclosed initializer list>)'
   48 |   ans.push_back({nowx,nowy});
      |   ~~~~~~~~~~~~~^~~~~~~~~~~~~
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:5:
/usr/include/c++/14/bits/stl_vector.h:1283:7: note: candidate: 'void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = r2; _Alloc = std::allocator<r2>; value_type = r2]'
 1283 |       push_back(const value_type& __x)
      |       ^~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1283:35: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'const std::vector<r2>::value_type&' {aka 'const r2&'}
 1283 |       push_back(const value_type& __x)
      |                 ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1300:7: note: candidate: 'void std::vector<_Tp, _Alloc>::push_back(value_type&&) [with _Tp = r2; _Alloc = std::allocator<r2>; value_type = r2]'
 1300 |       push_back(value_type&& __x)
      |       ^~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1300:30: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'std::vector<r2>::value_type&&' {aka 'r2&&'}
 1300 |       push_back(value_type&& __x)
      |                 ~~~~~~~~~~~~~^~~
a.cc: In function 'int main()':
a.cc:52:8: error: 'k' was not declared in this scope
   52 |   cin>>k>>x>>y;
      |        ^
a.cc:52:11: error: 'x' was not declared in this scope
   52 |   cin>>k>>x>>y;
      |           ^
a.cc:52:14: error: 'y' was not declared in this scope; did you mean 'yn'?
   52 |   cin>>k>>x>>y;
      |              ^
      |              yn
a.cc:64:8: error: 'Y' was not declared in this scope
   64 |   if(X>Y)swap(X,Y);
      |        ^
a.cc:68:14: error: 'Y' was not declared in this scope
   68 |     if((j-(X+Y))%2==0)sousai=(j-(X+Y))/2;
      |              ^
a.cc:78:9: error: 'nowx' was not declared in this scope
   78 |   while(nowx+k<=X)move(k,0);
      |         ^~~~
a.cc:79:9: error: 'nowy' was not declared in this scope
   79 |   while(nowy+k<=Y)move(0,k);
      |         ^~~~
a.cc:79:17: error: 'Y' was not declared in this scope
   79 |   while(nowy+k<=Y)move(0,k);
      |                 ^
a.cc:80:6: error: 'nowx' was not declared in this scope
   80 |   if(nowx!=X||nowy!=Y)ans.push_back({X,Y});
      |      ^~~~
a.cc:80:15: error: 'nowy' was not declared in this scope
   80 |   if(nowx!=X||nowy!=Y)ans.push_back({X,Y});
      |               ^~~~
a.cc:80:21: error: 'Y' was not declared in this scope
   80 |   if(nowx!=X||nowy!=Y)ans.push_back({X,Y});
      |                     ^
a.cc:80:36: error: no matching function for call to 'std::vector<r2>::push_back(<brace-enclosed initializer list>)'
   80 |   if(nowx!=X||nowy!=Y)ans.push_back({X,Y});
      |                       ~~~~~~~~~~~~~^~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1283:7: note: candidate: 'void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = r2; _Alloc = std::allocator<r2>; value_type = r2]'
 1283 |       push_back(const value_type& __x)
      |       ^~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1283:35: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'const std::vector<r2>::value_type&' {aka 'const r2&'}
 1283 |       push_back(const value_type& __x)
      |                 ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1300:7: note: candidate: 'void std::vector<_Tp, _Alloc>::push_back(value_type&&) [with _Tp = r2; _Alloc = std::allocator<r2>; value_type = r2]'
 1300 |       push_back(value_type&& __x)
      |       ^~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1300:30: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'std::vector<r2>::value_type&&' {aka 'r2&&'}
 1300 |       push_back(value_type&& __x)
      |                 ~~~~~~~~~~~~~^~~