#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 in_num = 0, out_num = 0;
    for( int i = 1; i <= N; i++ )
    {
        if( in[i] > out[i] )
        {
            in_num += in[i] - out[i];
        }
        else if( in[i] < out[i] )
        {
            out_num += out[i] - in[i];
        }
    }

    if( ( in_num == 0 && out_num == 0 ) || ( in_num == 1 && out_num == 1 ) )
    {
        cout << 0 << endl;
    }
    else
    {
        cout << in_num / 2 << endl;
    }

    return 0;
}