#include <bits/stdc++.h>
#define MaxN 100001
using namespace std;

ifstream fin("dfs.in");
ofstream fout("dfs.out");

int n, m, k, x, y;
bitset <MaxN> viz;

int main()
{
    cin >> n >> m;
    k = n;
    for(int i=1; i<=m; i++)
    {
        cin >> x >> y;
        if(viz[x] == 0 || viz[y] == 0)
        {
            k--;
        }

        viz[x] = viz[y] = 1;
    }

    cout << k;
}