#include<bits/stdc++.h>
#define N 510
#define M 20100
#define INF 0x3f3f3f3f 
using namespace std;
int head[N<<1];
int dep[N<<1];
struct node
{
    int from,to,val,next;
}edge[M];
int cnt,S,T,n,k;
void init()
{
    memset(head,-1,sizeof(head));
}
void edgeadd(int from,int to,int val)
{
    edge[cnt].from=from,edge[cnt].to=to;
    edge[cnt].val=val;
    edge[cnt].next=head[from];
    head[from]=cnt++;
}
int bfs(int s,int e)
{
    memset(dep,0,sizeof(dep));
    queue<int>q;
    q.push(s);
    dep[s]=1;
    while(!q.empty())
    {
        int u=q.front();
        q.pop();
        if(u==e)return 1;
        for(int i=head[u];i!=-1;i=edge[i].next)
        {
            int to=edge[i].to;
            if(dep[to]==0&&edge[i].val!=0)
            {
                dep[to]=dep[u]+1;
                q.push(to);
            }
        }
    }
    return 0;
}
int dfs(int s,int max_vale)
{
    int ret=0,tmp;
    if(s==n*2+1)return max_vale;
    for(int i=head[s];i!=-1;i=edge[i].next)
    {
        int to=edge[i].to;
        if(dep[to]!=dep[s]+1||edge[i].val==0)continue;
        tmp=dfs(to,min(max_vale-ret,edge[i].val));
        edge[i].val-=tmp;
        edge[i^1].val+=tmp;
        ret+=tmp; 
        if(ret==max_vale)return max_vale;
    }
    return ret;
}
int dinic()
{
    int ret=0;
    while(bfs(S,T))
    {
        while(int t=dfs(S,INF))
        {
            ret+=t;
        }
    }
    return ret;
}
int main()
{
    init();
    scanf("%d%d",&n,&k);
    S=0,T=n*2+1;
    for(int i=1;i<=k;i++)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        edgeadd(x,y+n,1);
        edgeadd(y+n,x,0);
    }
    for(int i=1;i<=n;i++)
    {
        edgeadd(S,i,1);
        edgeadd(i,S,0);
        edgeadd(i+n,T,1);
        edgeadd(T,i+n,0);
    }
    printf("%d\n",dinic());
    return 0;
}