#include <fstream>
#include <vector>
#include <queue>
using namespace std;
ifstream fin("drumuri2.in");
ofstream fout("drumuri2.out");
int const N = 401, inf = (1 << 30);
int n , m;
int st[N] , dr[N] , lv[N] , viz[N];
vector<int> v[N] , g[N];
void dfs1(int x , int t = -1){
    viz[x] = 1;
    for(int y : g[x]){
        if(t != y && !viz[y])
            dfs1(y , x);
    }
}
bool bfs(){
    queue<int> q;
    for(int i = 1 ; i <= n ; ++ i)
        if(!dr[i])
            q.push(i) , lv[i] = 0;
        else
            lv[i] = inf;
    lv[0] = inf;
    while(!q.empty()){
        int x = q.front();
        q.pop();
        if(lv[x] >= lv[0])
            continue;
        for(int y : v[x]){
            if(lv[st[y]] == inf){
                lv[st[y]] = 1 + lv[x];
                q.push(st[y]);
            }
        }
    }
    return lv[0] != inf;
}
bool dfs(int x){
    if(x == 0)
        return true;
    for(int y : v[x]){
        if(lv[st[y]] == 1 + lv[x] && dfs(st[y])){
            dr[x] = y;
            st[y] = x;
            return true;
        }
    }
    lv[x] = inf;
    return false;
}
int maxmatch(){
    int r = 0;
    while(bfs()){
        for(int i = 1 ; i <= n ; ++ i)
            if(!dr[i] && dfs(i))
                ++ r;
    }
    return r;
}
int main()
{
    fin >> n >> m;
    for(int i = 1 ; i <= m ; ++ i){
        int x , y;
        fin >> x >> y;
        g[x].push_back(y);
    }
    for(int i = 1 ; i <= n ; ++ i){
        for(int j = 1 ; j <= n ; ++ j)
            viz[j] = 0;
        dfs1(i);
        for(int j = 1 ; j <= n ; ++ j)
            if(viz[j] && j != i)
                v[i].push_back(j + n);
    }
    fout << n - maxmatch() << '\n';
    return 0;
}