#include<bits/stdc++.h>

using namespace std;

#define MAXN 510

#define MAXK 10010

struct edge

{

        int to,nxt;

} e[MAXK];

int n,k,i,r,c,ans,tot;

int head[MAXN],match[MAXN << ];

bool visited[MAXN << ];

inline void addedge(int u,int v)

{

        tot++;

        e[tot] = (edge){v,head[u]};

        head[u] = tot;

}

inline bool hungary(int u)

{

        int i,v;

        visited[u] = true;

        for (i = head[u]; i; i = e[i].nxt)

        {

                v = e[i].to;

                if (!visited[v])

                {

                        visited[v] = true;

                        if (!match[v] || hungary(match[v]))

                        {

                                match[v] = u;

                                return true;

                        }

                }

        }

        return false;

}

int main()

{

        scanf("%d%d",&n,&k);

        for (i = ; i <= k; i++)

        {

                scanf("%d%d",&r,&c);

                addedge(r,c + n);

        }

        for (i = ; i <= n; i++)

        {

                memset(visited,false,sizeof(visited));

                if (hungary(i)) ans++;

        }

        printf("%d\n",ans);

        return ;

}