Language: C++

#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<set>
#include<queue>
#include<stack>
#include<bitset>
#include<functional>
#include<map>
using namespace std;
/*int p = 998244353;*/
int p = 1000000007;
#define int long long
#define vel vector<long long>
#define vvel vector<vel>
#define rep(i,n) for(long long i=0;i<n;i++)
#define sor(v) sort(v.begin(),v.end())
#define mmax(a,b) a=max(a,b)
#define mmin(a,b) a=min(a,b)
#define mkp make_pair
#define pin pair<int,int>
#define qin pair<pin,int>
#define V vector
#define Endl endl
#define veb vector<bool>
#define sq(a) (a)*(a)
#define rev(s) reverse(s.begin(),s.end())
#define end_pr(s) cout << s <<endl;return 0
#define itn int
#define bs bitset<5001>

int kai_size = 2600001;
vel kai(kai_size, 1);
vel ink(kai_size, 1);
int RE() {
	vel v(3, 2);
	return v.at(4);
}
int ru(int a, int r) {
	if (r == 0) { return 1; }
	int ans = ru(a, r / 2);
	ans *= ans; ans %= p;
	if (r % 2 == 1) { ans *= a; }
	return ans % p;
}
int inv(int a) {
	return ru(a, p - 2);
}
void make_kai() {
	rep(i, kai_size - 1) { kai[i + 1] = (kai[i] * (i + 1)) % p; }
	rep(i, 1000001) { ink[i] = inv(kai[i]); }
}
int com(int n, int r) {
	int ans = kai[n] * ink[r];
	ans %= p; ans *= ink[n - r]; ans %= p;
	return ans;
}
vel dis(int mid1, vvel &way) {
	int n = way.size();
	vel dist(n, -1); dist[mid1] = 0;
	queue<int> q;
	q.push(mid1);
	while (!q.empty()) {
		int st = q.front(); q.pop();
		rep(i, way[st].size()) {
			int to = way[st][i];
			if (dist[to] == -1) {
				dist[to] = dist[st] + 1;
				q.push(to);
			}
		}
	}
	return dist;
}
pin most_far(int now, int n, vvel &way) {
	vel dist1 = dis(now, way);
	pin ans = mkp(-1, 0);
	rep(i, n) {
		if (dist1[i] > ans.first) { ans = mkp(dist1[i], i); }
	}
	return ans;
}

int per(int a, int b) {
	int ans = a % b;
	if (ans < 0) { ans += b; }
	return ans;
}
V<pin> uni(V<pin> &v) {
	sor(v);
	V<pin> ans(1, v[0]);
	for (int i = 1; i < v.size(); i++) {
		if (v[i] != v[i - 1]) { ans.push_back(v[i]); }
	}
	v = ans;
	return v;
}
int s_gcd(int a, int b) {
	if (b == 0) { return a; }
	return s_gcd(b, a%b);
}
int gcd(int a, int b) {
	if (a < b) { swap(a, b); }
	return s_gcd(a, b);
}
int sn(int n) {
	if (n >= 0) { return 1; }
	return -1;
}
V<pin> solve(int x,int y,int k,V<pin> &ans);
V<pin> solve1(int x, int y, int k);
V<pin> solve2(int x, int y, int k) {
	if (x + y == k) { return { mkp(x,y) }; }
	if (x+y<k) {
		if ((x + y) % 2 == 1) {
			V<pin> ans{ mkp(k,0)};
			V<pin> ans2 = solve1(k - x, y, k);
			rep(i,ans2.size()) {
				pin st = ans2[i];
				st.first *= -1;
				ans.push_back(st);
			}
			return ans;
		}
		int su = x + y; su /= 2;
		return { mkp(su - k,su),mkp(x - su + k,y - su) };
	}
	if ((x + y) % 2 == 1) {
		V<pin> ans{ mkp(0,k) };
		solve(x,y-k, k,ans);
		return ans;
	}
	int su = x + y; su /= 2;
	return { mkp(su - k,su),mkp(x - su + k,y - su) };
}
V<pin> solve1(int x, int y, int k) {
	V<pin> ans = solve2(min(x, y), max(x, y), k);
	if (x > y) {
		rep(i, ans.size()) {
			swap(ans[i].first, ans[i].second);
		}
	}
	return ans;
}
void solve(int x, int y, int k, V<pin> &ans) {
	if (abs(x) + abs(y) == k) { ans.push_back(mkp(x, y)); return; }
	V<pin> a = solve1(abs(x), abs(y), k);
	rep(i,a.size()) {
		pin st = a[i];
		st.first *= sn(x);
		st.second *= sn(y);
		ans.push_back(st);
	}
}
signed main() {
	int k, x, y; cin >> k >> x >> y;
	if (k % 2 == 0 and (abs(x) + abs(y)) % 2 == 1) { cout << -1 << endl; return 0; }
	V<pin> ans;
	while (abs(x) + abs(y) >= 2 * k) {
		if (abs(x) >= k) {
			int di = sn(x)*k;
			ans.push_back(mkp(sn(x)*k, 0));
			x -= di;
		}
		else {
			int di = sn(y)*k;
			ans.push_back(mkp(0, sn(y)*k));
			y -= di;
		}
	}
	solve(x, y, k, ans);
	cout << ans.size() << Endl;
	int mx = 0; int my = 0;
	rep(i, ans.size()) {
		pin xx = ans[i];
		mx += xx.first; my += xx.second;
		cout << mx << " " << my << endl;
	}
	return 0;
}


Compiler output:
a.cc:146:6: error: ambiguating new declaration of 'void solve(long long int, long long int, long long int, std::vector<std::pair<long long int, long long int> >&)'
  146 | void solve(int x, int y, int k, V<pin> &ans) {
      |      ^~~~~
a.cc:111:8: note: old declaration 'std::vector<std::pair<long long int, long long int> > solve(long long int, long long int, long long int, std::vector<std::pair<long long int, long long int> >&)'
  111 | V<pin> solve(int x,int y,int k,V<pin> &ans);
      |        ^~~~~