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

const int maxn = 2e4;
int deg[maxn];
int S, cnd;
int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int N, M; cin >> N >> M;

    for (int i = 0; i < M; ++i) {
        int a, b; cin >> a >> b;
        deg[a] += 1;
        deg[b] += 1;
    }

    for (int x = 0; x < N; ++x) deg[x]--;

    vector<int> ids(N); iota(ids.begin(), ids.end(), 0);
    sort(ids.begin(), ids.end(), [&](const auto& l, const auto& r) {
        return deg[l] < deg[r];
    });

    for (int i = 0; i < N; ++i) {
        if (S + deg[ids[i]] > N-2) break;
        S += deg[ids[i]];
        cnd += 1;
    }

    cout << N-cnd << '\n';
    cout << N << ' '  << N-1 << '\n';

    for (int i = cnd; i < N; ++i) {
        if (S == N-2) deg[ids[i]] = 0;
        else {
            deg[ids[i]] = 1;
            S += 1;
        }
    }

    sort(ids.begin(), ids.end(), [&](const auto& l, const auto& r) {
        return deg[l] < deg[r];
    });

    int j = 0;
    for (int i = 0; i+2 < N; ++i) {
        while (deg[ids[j]] == 0) j += 1;
        deg[ids[j]] -= 1;
        cout << ids[i] << ' ' << ids[j] << '\n';
    }

    cout << ids[N-2] << ' ' << ids[N-1] << '\n';
}