#include <bits/stdc++.h>
using namespace std;
void build(vector<int> u, vector<int> v, vector<int> a, vector<int> b);
int construct_roads(vector<int> x, vector<int> y) {
const int n = x.size();
vector<int> ord(n);
iota(ord.begin(), ord.end(), 0);
sort(ord.begin(), ord.end(), [&](int i, int j) { return y[i] < y[j]; });
for (int i = 1; i < n; ++i) {
if (y[ord[i]] - y[ord[i - 1]] != 2) {
return 0;
}
}
vector<int> u, v, a, b;
for (int i = 1; i < n; ++i) {
u.push_back(ord[i - 1]), v.push_back(ord[i]);
a.push_back(x[ord[i - 1]] + 1), b.push_back(y[ord[i - 1]] + 1);
}
build(u, v, a, b);
return 1;
}
