#include <cstdio>
#include <cstring>
#include <vector>
#include <queue>
#include <stack>
#include <cmath>
using namespace std;
const int maxn = 3010;
const int INF = 1<<28;
int dx[maxn], dy[maxn];
int cx[maxn], cy[maxn];
vector <int> G[maxn];
int dis;
int n, m;
bool vis[maxn];
bool search()
{
	queue <int> Q;
	int dis = INF;
	memset(dx, -1, sizeof(dx));
	memset(dy, -1, sizeof(dy));
	for(int i = 0; i < n; i++)
		if(cx[i] == -1)
		{
			Q.push(i);
			dx[i] = 0;
		}
	while(!Q.empty())
	{
		int u = Q.front(); Q.pop();
		if(dx[u] > dis)
			break;
		for(int i = 0; i < G[u].size(); i++)
		{
			int v = G[u][i];
			if(dy[v] == -1)
			{
				dy[v] = dx[u] + 1;
				if(cy[v] == -1)
					dis = dy[v];
				else
				{
					dx[cy[v]] = dy[v] + 1;
					Q.push(cy[v]);
				}
			}
		}
	}
	return dis != INF;
}

bool dfs(int u)
{
	for(int i = 0; i < G[u].size(); i++)
	{
		int v = G[u][i];
		if(vis[v])
			continue;
		vis[v] = true;
		if(dy[v] == dx[u]+1)
		{
			if(cy[v] != -1 && dy[v] == dis)
				continue;
			if(cy[v] == -1 || dfs(cy[v]))
			{
				cy[v] = u;
				cx[u] = v;
				return true;
			}
		}
	}
	return false;
}
int match()
{
    int ans = 0;
    memset(cx, -1, sizeof(cx));
    memset(cy, -1, sizeof(cy));
    while(search())
    {
		memset(vis, 0, sizeof(vis));
		for(int i = 0; i < n; i++)
			if(cx[i] == -1 && dfs(i))
		    	ans++;
    }
    return ans;
}