struct tarjan
{
	const int maxn=50050;
	vector<int>v[maxn];
	stack<int>S;
	int dfn[maxn],low[maxn],viss[maxn];
	int index,cnt;
	void init(int n)
	{
		for(int i=0;i<=n;i++)
		v[i].clear();
		memset(dfn,0,sizeof(dfn));
		memset(low,0,sizeof(low));
		memset(viss,0,sizeof(viss));
		index=0,cnt=0;
	}
	void dfs(int x)
	{
		dfn[x]=low[x]=++index;
		S.push(x);
		for(int i=0;i<v[x].size();i++)
		{
			int y=v[x][i];
			if(!dfn[y])
			{
				dfs(y);
				low[x]=min(low[x],low[y]);
			}
			else if(!viss[y])
			{
				low[x]=min(low[x],dfn[y]);
			}
		}
		if(dfn[x]==low[x])
		{
			cnt++;
			while(1)
			{
				int s=S.top();S.pop();
				viss[s]=cnt;                //縮點 
				if(s==x)
				break;
			}
		}
	}
	void solve(int n)
	{
		init();
		for(int i=1;i<=n;i++)
		{
			if(!dfn[i])
			dfs(i);
		}
	}
}T;