#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxm = 40010;
const int maxn = 1010;
int first[maxn], cnt;
struct edge
{
	int u, v, next;
}e[maxn*maxn];
int ans[maxm];
bool vis[maxm];
int len;
void AddEdge(int u, int v)
{
	e[cnt].u = u;
	e[cnt].v = v;
	e[cnt].next = first[u];
	first[u] = cnt++;
}

void dfs(int u)
{
	for(int i = first[u]; i != -1; i = e[i].next)
	{
		if(!vis[i])
		{
			vis[i] = true;
			dfs(e[i].v);
			ans[len++] = i;
		}
	}
}

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