#include <iostream>
#include <queue>
#include <cstring>
#include <stack>
#include <fstream>
using namespace std;
typedef long long ll;
const int maxn = 667;
bool graph[maxn][maxn];
bool visited[maxn];
int match[maxn];
int n, k;

bool dfs(int node) {
    for(int i = 0; i < n; i++) {
        if(graph[node][i] and !visited[i]) {
            visited[i] = true;

            if(match[i] == -1 or dfs(match[i])) {
                match[i] = node;
                return true;
            }
        }
    }
    return false;
}
int maximum_bipartite_matching() {
    memset(match, -1, sizeof match);
    int result = 0;

    for(int i = 0; i < n; i++) {
        memset(visited, false, sizeof visited);
        if(dfs(i)) {
            result++;
        }
    }
    return result;
}
int main() {
    ios_base::sync_with_stdio(false);
    cin >> n >> k;
    memset(graph, true, sizeof graph);
    for(int i = 0; i < k; i++) {
        int a, b;
        cin >> a >> b;
        a--; b--;
        graph[a][b] = false;

    }
    cout << maximum_bipartite_matching() << endl;
    return 0;
}