#include <bits/stdc++.h>
#define pb push_back
#define N  8195
using namespace std;

vector<int>v[N];
int l[N], r[N], n, m, sol, x, y, ok, i;
bitset<N>viz;
bool pairup(int nod)
{
    if(viz[nod])
        return 0;
    for(auto it : v[nod])
        if(!r[it] || pairup(r[it]))
        {
            l[nod] = it;
            r[it] = nod;
            return 1;
        }
    return 0;
}
int main()
{
    freopen("felinare.in", "r", stdin);
    freopen("felinare.out", "w", stdout);
    scanf("%d%d", &n, &m);
    for(; m; m--)
    {
        scanf("%d%d", &x, &y);
        v[x].pb(y);
    }
    for(ok = 1; ok;)
    {
        ok = 0;
        viz = 0;
        for(i = 1; i <= n; i++)
            if(!l[i] && pairup(i))
            {
                sol++;
                ok = 1;
            }
    }
    printf("%d\n", sol);
    return 0;
}