#include<cstdio>

#include<cstring>

inline int read()

{

    int x;char c;

    while((c=getchar())<''||c>'');

    for(x=c-'';(c=getchar())>=''&&c<='';)x=(x<<)+(x<<)+c-'';

    return x;

}

#define MN 100

#define MM 1000

#define MV 200

#define ME 10000

#define S MV+1

#define T MV+2

#define INF 0x7FFFFFFF

namespace MaxFlow

{

    struct edge{int nx,t,w;}e[ME*+];

    int h[MV+],en=,d[MV+],q[MV+],qn,c[MV+];

    inline void ins(int x,int y,int w)

    {

        e[++en]=(edge){h[x],y,w};h[x]=en;

        e[++en]=(edge){h[y],x,};h[y]=en;

    }

    bool bfs()

    {

        int i,j;

        memset(d,,sizeof(d));

        for(d[q[i=qn=]=S]=;i<=qn;++i)for(j=c[q[i]]=h[q[i]];j;j=e[j].nx)

            if(e[j].w&&!d[e[j].t])d[q[++qn]=e[j].t]=d[q[i]]+;

        return d[T];

    }

    int dfs(int x,int r)

    {

        if(x==T)return r;

        int k,u=;

        for(int&i=c[x];i;i=e[i].nx)if(e[i].w&&d[e[i].t]==d[x]+)

        {

            k=dfs(e[i].t,r-u<e[i].w?r-u:e[i].w);

            u+=k;e[i].w-=k;e[i^].w+=k;

            if(u==r)return r;

        }

        return d[x]=,u;

    }

    int dinic(){int ans=;while(bfs())ans+=dfs(S,INF);return ans;}

};

struct edge{int nx,t;}e[MM+];

int h[MN+],en,q[MN+],qn,u[MN+];

inline void ins(int x,int y){e[++en]=(edge){h[x],y};h[x]=en;}

int main()

{

    int n,m,i,j,k,x,y;

    n=read();m=read();

    while(m--)x=read(),y=read(),ins(x,y);

    using MaxFlow::ins;

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

    {

        ins(S,i,);ins(i+n,T,);

        memset(u,,sizeof(u));

        for(u[q[j=qn=]=i]=;j<=qn;++j)for(k=h[q[j]];k;k=e[k].nx)

            if(!u[e[k].t])ins(i,e[k].t+n,INF),u[q[++qn]=e[k].t]=;

    }

    printf("%d",n-MaxFlow::dinic());

}