#include<iostream>
#include<vector>

using namespace std;

int main( void )
{
    int N, M;
    cin >> N >> M;
    vector<int> in( N + 1, 0 ), out( N + 1, 0 );
    
    int u, v;
    for( int i = 0; i < M; i++ )
    {
        cin >> u >> v;
        if( u == v ) continue;
        in[v]++, out[u]++;
    }

    int num = 0;
    for( int i = 1; i <= N; i++ )
    {
        num += abs( in[i] - out[i] );
    }

    if( num == 0 || num == 2 )
    {
        cout << 0 << endl;
    }
    else
    {
        cout << num / 2 - 1 << endl;
    }

    return 0;
}