#include<iostream>
#include<vector>
#define endl '\n'
using namespace std;
typedef long long ll;
int n,k;
vector<int> g[510];
int match[510]={};
bool find(int i)
{
	for(int j=0;j<g[i].size();j++)
	{
		int &m=match[g[i][j]];
		if(m==0 || m!=i && find(m))
		{
			m=i;
			return true;
		}
	}
	return false;
}
int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
 
	cin>>n>>k;
	for(int i=0;i<k;i++)
	{
		int a,b;
		cin>>a>>b;
		g[a].push_back(b);
	}
	int ans=0;
	for(int i=1;i<=n;i++)
		if(find(i))
			ans++;
	cout<<ans<<endl;
}

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MyA0CjEgMQoxIDMKMiAyCjMgMgo=

3 4
1 1
1 3
2 2
3 2