#include <iostream>
using namespace std;


int G[1005][505];//邻接表
int deg[1005];//每个节点的度
int match[1005];//与节点配对的节点
bool used[505];//记录节点是否已被搜索过

bool dfs(int v);//利用二分图的性质优化dfs

int main()
{
	int N, K, R, C, ans = 0;

	cin >> N >> K;

	for (int i = 0; i < K; i++)
	{
		cin >> R >> C;

		G[R][deg[R]++] = N + C;
		G[N + C][deg[N + C]++] = R;
	}

	for (int i = 1; i <= N; i++)
	{
		for (int i = 1; i <= N; i++)
		{
			used[i] = false;
		}
		if (dfs(i))
		{
			ans++;
		}		
	}

	cout << ans << '\n';

	return 0;
}

bool dfs(int v)
{
	int u, w;//用于临时记录

	used[v] = true;

	for (int i = 0; i < deg[v]; i++)
	{
		u = G[v][i];
		w = match[u];

		if (!w)
		{
			match[v] = u;
			match[u] = v;
			return true;
		}
		else if (!used[w])
		{
			if (dfs(w))
			{
				match[v] = u;
				match[u] = v;
				return true;
			}
		}
	}
	return false;
}