#include <fstream>
#include <vector>
#include <stack>
#define MAX 100004

using namespace std;

vector<int> v[MAX];
vector<int> q;
int n, m;
int vis[MAX];

void read();
void dfs();
bool checkStack(int x);

int main()
{
    read();
    dfs();
    return 0;
}

void read(){
    ifstream fin ("dfs.in");
    fin >> n >> m;
    int x, y;
    for (int i = 1; i <= m; ++i){
        fin >> x >> y;
        v[x].push_back(y);
        v[y].push_back(x);
    }
    fin.close();
}

void dfs(){
    int k(0);
    q.push_back(1);
    while(!q.empty()){

        int u = q.back();
        q.pop_back();

        if (!vis[u] && checkStack(u))
        {
            ++k;
            vis[u] = 1;
            for (unsigned int i = 0; i < v[u].size(); ++i)
                if (!vis[v[u][i]])
                    q.push_back(v[u][i]);
        }
    }

    ofstream fout ("dfs.out");
    fout << k;
    fout.close();
}

bool checkStack(int x){
    for (unsigned int i = 0; i < q.size(); ++i)
        if (q[i] == x)
            return 0;
    return 1;
}