#include<iostream>

#include<cstdio>

#include<cstring>

#define maxn 2020

using namespace std;

int n,m,g[maxn][maxn],ans,f[maxn],match[maxn];

int init()

{

    int x=;char s;s=getchar();

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

    while(s>=''&&s<=''){x=x*+s-'';s=getchar();}

    return x;

}

int Dfs(int s)

{

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

      if(g[s][i]&&f[i]==)

        {

          f[i]=;

          if(match[i]==||Dfs(match[i]))

            {

              match[i]=s;

              return ;

            }

        }

    return ;

}

int main()

{

    n=init();m=init();

    int x,y;

    for(int i=;i<=m;i++)

      {

        x=init();y=init();

        g[x][y]=;

      }

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

      {

        memset(f,,sizeof(f));

        ans+=Dfs(i);

      }

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

    return ;

}