#include <iostream>
#include <stdio.h>
#include <vector>
#include <cstring>
#define NMax 8200
using namespace std;
vector<int> Graf[NMax];
int N,M,x,y,CuplajMaxim;
int F1[NMax];
int F2[NMax];
bool mark[NMax],cuplaj;

void Read()
{
    scanf("%d%d",&N,&M);
    for(int i=1;i<=M;i++)
    {
        scanf("%d%d",&x,&y);
        Graf[x].push_back(y);
    }
}

bool  Cuplaj(int x)
{
    if(mark[x])
        return false;
    mark[x]=true;
    for(vector<int>::iterator it=Graf[x].begin();it!=Graf[x].end();it++)
        if(F2[*it]==0)
        {
            F1[x]=*it,F2[*it]=x;
            return true;
        }
    for(vector<int>::iterator it=Graf[x].begin();it!=Graf[x].end();it++)
        if(Cuplaj(F2[*it]))
        {
            F1[x]=*it,F2[*it]=x;
            return true;
        }
    return false;
}

void Solve()
{
    cuplaj=true;
    while(cuplaj==true)
    {
        cuplaj=false;
        memset(mark,false,sizeof(mark));
        for(int i=1;i<=N;i++)
        if(F1[i]==0 && Cuplaj(i)==true)
        {
            cuplaj=true;
            CuplajMaxim++;
        }
    }
}

inline void Write()
{
   printf("%d",2*N-CuplajMaxim);
}

int main()
{
    freopen("felinare.in","r",stdin);
    freopen("felinare.out","w",stdout);
    Read();
    Solve();
    Write();
}