#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <array>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <sstream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <list>
#include <numeric>
#include <stack>
#include <iomanip>
#include <random>
#include <complex>
#include <functional>
#include <tuple>

using namespace std;

#define Rep(i,a,b) for(ll i = a; i < b; ++i)
#define rep(i,b) Rep(i,0,b)
#define allof(a) (a).begin(), (a).end()

#define Yes(q) ((q) ? "Yes" : "No")
#define YES(q) ((q) ? "YES" : "NO")
#define Possible(q) ((q) ? "Possible" : "Impossible")
#define POSSIBLE(q) ((q) ? "POSSIBLE" : "IMPOSSIBLE")

using ll = long long;

constexpr int inf = 1e9 + 7;
constexpr ll infll = 1ll << 60ll;
constexpr ll mod = 1e9 + 7;
// 0~3までは右左下上 4~7までは斜め
constexpr int dx[] = { 1, 0, -1, 0, 1, 1, -1, -1 };
constexpr int dy[] = { 0, -1, 0, 1, 1, -1, -1, 1 };

namespace {
    template<typename T> void chmax(T& a, T b) { a = std::max(a, b); }
    template<typename T> void chmin(T& a, T b) { a = std::min(a, b); }
    template<typename T> void chadd(T& a, T b) { a = a + b; }

    void Cout(long long x, const char* end = "\n") { std::cout << x << end; }
    template <typename T> void Cout(const T& x, const char* end = "\n") { std::cout << x << end; }
    template <typename T> void Cout(const std::vector<T>& x, const char* sep = " ", const char* end = "\n") { for (std::size_t i = 0, sz = x.size(); i < sz; i++) { std::cout << x[i] << (i == sz - 1 ? end : sep); } }

    // 標準入出力
    struct inp {
        std::size_t sz;
        inp(std::size_t _sz = 1) : sz(_sz) {}
        template <typename T> operator T () const { T a; std::cin >> a; return a; }
        template <typename T> operator std::vector<T>() const { std::vector<T> a(sz); for (std::size_t i = 0; i < sz; i++) std::cin >> a[i]; return a; }
    };

    // 2次元用の標準入出力
    template<typename T>
    struct inpn {
        std::size_t szi, szj;
        inpn(std::size_t _szi, std::size_t _szj) : szi(_szi), szj(_szj) {}
        operator std::vector<std::vector<T>>() const {
            std::vector<std::vector<T>> a(szi, std::vector<T>(szj));
            for (std::size_t i = 0; i < szi; ++i)
                for (std::size_t j = 0; j < szj; ++j) cin >> a[i][j];
            return a;
        }
    };

    inp inp1; // input one

    // ダイクストラ法
    vector<ll> dijkstra(ll start, vector<vector<pair<int, int>>>& G, int n) {
        vector<ll> dist(n, infll);
        dist[start] = 0; // dist[i] := start->iまでの最短距離
        priority_queue < pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>> que;
        que.push({ 0, start });
        while (!que.empty()) {
            ll cost, u; // 今までにかかった時間　現在の頂点
            cost = que.top().first, u = que.top().second;
            que.pop();
            if (dist[u] < cost) continue;
            for (auto tmp : G[u]) {
                ll v = tmp.first, time = tmp.second; // 隣接する頂点、その頂点まで行く時間
                if (dist[v] > dist[u] + time) {
                    dist[v] = dist[u] + time;
                    que.push({ dist[v], v });
                }
            }
        }
        return dist;
    }
}


int main() {

    vector<int> ans;

    while (true) {
        int n, m;
        cin >> n >> m;
        if (n == 0 && m == 0) break;

        vector<int> a(m), b(m);
        rep(i, m) cin >> a[i] >> b[i];

        vector<vector<pair<int, int>>> g(n);
        rep(i, m) {
            g[a[i] - 1].push_back({ b[i] - 1, 1 });
            g[b[i] - 1].push_back({ a[i] - 1, 1 });
        }

        auto dist = dijkstra(0, g, n);
        int res = 0;
        Rep(i, 1, n) {
            if (dist[i] <= 2) ++res;
        }
        ans.emplace_back(res);
    }

    rep(i, ans.size()) {
        Cout(ans[i]);
    }


    return 0;
}


Measured memory_bytes: 3328