#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ld, ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;

#define FOR(i, a, b) for (int i = a; i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b) - 1; i >= (a); i--)
#define F0Rd(i, a) for (int i = (a) - 1; i >= 0; i--)
#define trav(a, x) for (auto &a : x)
#define sz(x) (int)(x).size()
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define ins insert

const char nl = '\n';

void solve() {
	int N, M; cin >> N >> M;
	vpi deg(N); F0R(i, N) deg[i].s = i;
	F0R(i, M) {
		int X, Y; cin >> X >> Y; 
		deg[X].f++; deg[Y].f++;
	}
	sort(all(deg));
	int tot = 0;
	int cnt = N;
	F0R(i, N) {
		tot += deg[i].f;
		if (tot + N-i-1 > 2*N-2) {
			cnt = i;
			break;
		}
	}
	int nd[N]; F0R(i, N) nd[i] = 0;
	bool keep[N]; F0R(i, N) keep[i] = false;
	cout << N - cnt << nl;
	cout << N << " " << N-1 << nl;
	tot = 0;
	F0R(i, cnt) {
		keep[deg[i].s] = true;
		nd[deg[i].s] = deg[i].f;
		tot += deg[i].f;
	}
	int rem = 2*N-2-tot;
	while (rem > 0) {
		F0R(i, N) {
			if (!keep[i] && rem > 0) {
				rem--;
				nd[i]++;
			}
		}
	}
	set<pi> degs;
	F0R(i, N) {
		degs.ins({nd[i], i});
	}
	while (sz(degs) >= 2) {
		pi X = *degs.begin(), Y = *degs.rbegin();
		cout << X.s << " " << Y.s << nl;
		degs.erase(X); degs.erase(Y);
		degs.ins({Y.f-1, Y.s});
	}
}

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0);
	solve();
	return 0;
}