#include<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
#include<cstdio>
using namespace std;

const int MAXN = 1210;
const int MAXM = 21000;
const int INF = 0x3f3f3f3f;

struct Edge
{
	int from, to, cap, next;
};

Edge edge[MAXM];
int level[MAXN];
int head[MAXN];
int src, des, cnt;

void addedge(int from,int to,int cap)
{
	edge[cnt].from = from;
	edge[cnt].to = to;
	edge[cnt].cap = cap;
	edge[cnt].next = head[from];
	head[from] = cnt++;

	swap( from, to );

	edge[cnt].from = from;
	edge[cnt].to = to;
	edge[cnt].cap = 0;
	edge[cnt].next = head[from];
	head[from] = cnt++;
}

int bfs()
{
	memset( level, -1, sizeof level );
	queue<int> q;
	while(!q.empty())
		q.pop();

	level[src] = 0;
	q.push( src );

	while(!q.empty())
	{
		int u = q.front();
		q.pop();

		for(int i = head[u]; i != -1; i = edge[i].next)
		{
			int v = edge[i].to;
			if(edge[i].cap&&level[v] == -1)
			{
				level[v] = level[u] + 1;
				q.push( v );
			}
		}
	}
	return level[des] != -1;
}

int dfs( int u, int f )
{
	if(u == des)
		return f;
	int tem;
	for(int i = head[u]; i != -1; i = edge[i].next)
	{
		int v = edge[i].to;
		if(edge[i].cap > 0 && level[v] == level[u] + 1)
		{
			tem = dfs( v, min( f, edge[i].cap ) );
			if(tem > 0)
			{
				edge[i].cap -= tem;
				edge[i^1].cap += tem;
				return tem;
			}
		}
	}
	level[u] = -1;
		return 0;
}

int Dinic()
{
	int ans = 0, tem;
	while(bfs())
	{
		while((tem = dfs( src, INF ) > 0))
		{
			ans += tem;
		}
	}
	return ans;
}

int main()
{
	int n, k;
	src = 0; des = 1205;
	while(cin >> n >> k)
	{
		memset( head, -1, sizeof head );
		cnt = 0;
		for(int i = 1; i <= n; i++)
		{
			addedge( src, i, 1 );
			addedge( i + 500, des, 1 );
		}
		for(int i = 1; i <= k; i++)
		{
			int a, b;
			cin >> a >> b;
			addedge( a, b + 500, 1 );
		}

		cout << Dinic() << endl;
	}

	return 0;
}