#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>#include <climits>#include <string>#include <iostream>#include <map>#include <cstdlib>#include <list>#include <set>#include <queue>#include <stack>using namespace std;typedef long long LL;const int maxn = 505;int n,m,bx[maxn],by[maxn];bool vis[maxn],g[maxn][maxn];int dfs(int now) {    for(int i = 1;i <= n;i++) if(!vis[i] && g[now][i]) {        vis[i] = true;        if(!by[i] || dfs(by[i])) {            bx[now] = i; by[i] = now; return 1;        }    }    return 0;}int main() {    while(scanf("%d%d",&n,&m) != EOF) {        memset(g,0,sizeof(g));        memset(bx,0,sizeof(bx));        memset(by,0,sizeof(by));        for(int i = 1;i <= m;i++) {            int a,b; scanf("%d%d",&a,&b);            g[a][b] = true;        }        int ans = 0;        for(int i = 1;i <= n;i++) if(!bx[i]) {            memset(vis,0,sizeof(vis));            if(dfs(i)) ans++;        }        printf("%d\n",ans);    }    return 0;}