#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
const int maxn = 150;
int graph[maxn][maxn];
bool visited[maxn];
int match[maxn];
int n;
bool dfs(int node) {
    for(int i = 0; i < maxn; i++) {
        if(graph[node][i] == 1 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) == true) {
            result++;
        }
    }
    return result;
}
int main() {
   int  m;
    cin >> n >> m;
    memset(graph, 0, sizeof graph);
    for(int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        graph[a][b] = 1;
    }
    cout << maximum_bipartite_matching() << endl;
    return 0;
}
/*
 10 9
 1 6
 1 9
 1 10
 2 6
 2 7
 3 7
 4 8
 4 9
 5 10
 */