Sgu/174

//by hza
#include<cstdio>
#include<map>
using namespace std;
 
const int MAX=200000+10;
int n;
int fa[MAX*2];
int tot;
 
map<pair<int,int>,int>coor; 
 
int findfather(int i)
{
	if(i==fa[i])return i;
	else return fa[i]=findfather(fa[i]);
}
 
int main()
{
	#ifndef ONLINE_JUDGE
	freopen("174.in","r",stdin);freopen("174.out","w",stdout);
	#endif
	int sx,sy,tx,ty,i,fs,ft;
	scanf("%d",&n);
	for(i=1;i<=MAX*2-1;++i)fa[i]=i;
	for(i=1;i<=n;++i)
	{
		scanf("%d %d %d %d",&sx,&sy,&tx,&ty);
		pair<int,int>s(sx,sy);
		pair<int,int>t(tx,ty);
		if(!coor[s])coor[s]=++tot;
		if(!coor[t])coor[t]=++tot;
		fs=findfather(coor[s]);
		ft=findfather(coor[t]);
		if(fs==ft)
		{
			printf("%d\n",i);
			return 0;
		}else
			fa[fs]=ft;
	}
	printf("0\n");
	return 0;
}