#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<algorithm>
#define rep(i,x,y) for(register int i=x;i<=y;++i)
#define repd(i,x,y) for(register int i=x;i>=y;--i)
#define ll long long
using namespace std;
const int N=1e5+7;
struct {
    int v,nxt;
    inline void init(int a,int b){v=a; nxt=b;}
}e[N];
int head[N],cnt=1,vis[N],mark[N],n,m,ans;
template <typename T>inline void read(T &x){
    char c;int sign=1;x=0;
    do{c=getchar(); if(c=='-')sign=-1;}while(c<'0'||c>'9');
    do{x=x*10+c-'0'; c=getchar();}while(c>='0'&&c<='9');
    x*=sign;
}

void reade(int a,int b){e[cnt].init(b,head[a]); head[a]=cnt++;}

int find(int u){
    for(int i=head[u];i;i=e[i].nxt)if(!vis[e[i].v]){
        vis[e[i].v]=1;
        if(!mark[e[i].v]||find(mark[e[i].v])){
            mark[e[i].v]=u;
            return 1;
        }
    }
    return 0;
}

int main(){
    while(~scanf("%d%d",&n,&m)){
        ans=0;
        memset(head,0,sizeof(head));
        memset(mark,0,sizeof(mark));
        rep(i,1,m){
            int x,y;
            read(x);read(y);
            reade(x,y);
        }
        rep(i,1,n){
            memset(vis,0,sizeof(vis));
            ans+=find(i);
        }
        printf("%dn",ans);
    }
    return 0;
}