#include<iostream>

#include<cstdio>

#include<cstring>

#include<algorithm>

#define maxn 210

#define maxm 30010

using namespace std;

inline int read()

{

    int x=;

    bool f=;

    char c=getchar();

    for(; !isdigit(c); c=getchar()) if(c=='-') f=;

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

    if(f) return x;

    return -x;

}

inline void write(int x)

{

    if(x<){putchar('-');x=-x;}

    if(x>)write(x/);

    putchar(x%+'');

}

int n,m,ans,match[maxm],cnt,tc[maxn][maxn];

bool book[maxm];

inline bool dfs(int u)

{

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

    {

        if(tc[u][i]==)

        {

            if(!book[i])

            {

                book[i]=;

                if(!match[i]||dfs(match[i]))

                {

                    match[i]=u;

                    return true;

                }

            }

        }

    }

    return false;

}

int main()

{

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

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

    {

        int x,y;

        x=read();y=read();

        tc[x][y]=;

    }

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

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

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

                if(i!=j&&tc[i][j]==)

                {

                    tc[i][j]=tc[i][j]||(tc[i][k]&&tc[k][j]);

                }

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

    {

        memset(book,,sizeof(book));

        if(dfs(i))ans++;

    }

    write(n-ans);

    return ;

}