#include <cstdio>
#include <cstring>
using namespace std;
const int N = 550;

int g[N][N]; // 地图
int n, m;

// 匈牙利
int st[N], match[N];
int dfs(int u) {
    for (int i = 1; i <= n; i++) {
        if (g[u][i] && !st[i]) { // u->i有边
            st[i] = 1;
            if (match[i] == -1 || dfs(match[i])) {
                match[i] = u;
                return 1;
            }
        }
    }
    return 0;
}
int main() {
#ifndef ONa_JUDGE
    freopen("POJ3041.in", "r", stdin);
#endif
    memset(g, 0, sizeof g);
    memset(match, -1, sizeof match);
    scanf("%d%d", &n, &m);

    while (m--) {
        int x, y;
        scanf("%d%d", &x, &y);
        g[x][y] = 1;
    }

    // 匈牙利
    int res = 0;
    for (int i = 1; i <= n; i++) {
        memset(st, 0, sizeof st);
        if (dfs(i)) res++;
    }
    // 输出
    printf("%d\n", res);
    return 0;
}