#include <iostream>#include <cstdio>#include <utility>#include <map>using namespace std;typedef pair<int, int> ii;map<ii, int> f;int fa[400009];int n, xa, ya, xb, yb, cnt;int Find (int x) {	if (fa[x] != x) return fa[x] = Find (fa[x]);	return x;}int main() {	scanf ("%d", &n);	for (int i = 1; i <= 2 * n; i++) fa[i] = i;	for (int i = 1; i <= n; i++) {		scanf ("%d %d %d %d", &xa, &ya, &xb, &yb);		ii tem1 = make_pair (xa, ya), tem2 = make_pair (xb, yb);		if (f.count (tem1) == 0 ) f[tem1] = ++cnt;		if (f.count (tem2) == 0 ) f[tem2] = ++cnt;		int x = Find (f[tem1]), y = Find (f[tem2]);		if (x != y)			fa[x] = y;		else {			cout << i << endl;			return 0;		}	}	cout << 0 << endl;	return 0;}