#include<iostream>
#include<stack>
#include<vector>
#include<cstring>
#include<string>
#include<algorithm>
#include<cmath>
#include<cstdio>
#include<queue>
#define MAX_S (1<<10)+10
#define MAX_V 1234
#define MAX_N MAX_V
#define INF 1000009
using namespace std;

struct edge {
    int to, cap, rev;
    bool isRev;

    edge(int t, int c, int r, bool i)
            : to(t), cap(c), rev(r), isRev(i) { }

    edge() { }
};

template <class T>
inline bool scan_d(T &ret)
{
    char c;
    int sgn;
    if(c=getchar(),c==EOF) return 0; //EOF
    while(c!=‘ -‘ &&(c<‘0‘ ||c>‘9‘ )) c=getchar();
    sgn=(c==‘ -‘ )?-1:1;
    ret=(c==‘ -‘ )?0:(c-‘0‘ );
    while(c=getchar(),c>=‘0‘ &&c<=‘9‘ ) ret=ret*10+(c-‘0‘ );
    ret*=sgn;
    return 1;
}

vector<edge> G[MAX_N];
int level[MAX_V];
int iter[MAX_V];

void init(int totNode) {
    for (int i = 0; i <= totNode; i++)
        G[i].clear();
    memset(level, 0, sizeof(level));
    memset(iter, 0, sizeof(iter));
}

void add_edge(int from,int to,int cap) {
    G[from].push_back(edge (to, cap, G[to].size(),0));
    G[to].push_back(edge (from, 0, G[from].size() - 1,1));
}

void bfs(int s) {
    queue<int> que;
    memset(level, -1, sizeof(level));
    level[s] = 0;
    que.push(s);
    while (!que.empty()) {
        int v = que.front();
        que.pop();
        for (int i = 0; i < G[v].size(); i++) {
            edge &e = G[v][i];
            if (e.cap > 0 && level[e.to] < 0) {
                level[e.to] = level[v] + 1;
                que.push(e.to);
            }
        }
    }
}

int dfs(int v,int t,int f) {
    if (v == t)return f;
    for (int &i = iter[v]; i < G[v].size(); i++) {
        edge &e = G[v][i];
        if (e.cap > 0 && level[v] < level[e.to]) {
            int d = dfs(e.to, t, min(f, e.cap));
            if (d > 0) {
                e.cap -= d;
                G[e.to][e.rev].cap += d;
                return d;
            }
        }
    }
    return 0;
}

int max_flow(int s,int t) {
    int flow = 0;
    for (; ;) {
        bfs(s);
        if (level[t] < 0)return flow;
        memset(iter, 0, sizeof(iter));
        int f;
        while ((f = dfs(s, t, INF)) > 0) {
            flow += f;
        }
    }
}

int n,m;
int S=1233,T=1212;

int main() {
    cin.sync_with_stdio(false);
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        add_edge(u, v+n, 1);
    }
    for (int i = 1; i <= n; i++) {
        add_edge(S, i, 1);
        add_edge(i+n, T, 1);
    }
    cout << max_flow(S, T) << endl;
    return 0;
}