#include <bits/stdc++.h> using namespace std; using ll = long long; int main() { ll N, M; cin >> N >> M; vector<vector<ll> > adjList(N); for (ll i = 0; i < M; i++) { ll u, v; cin >> u >> v; adjList[u].push_back(v); adjList[v].push_back(u); } cout << N << endl; for (ll i = 0; i < N; i++) { cout << i << " " << (i + 1) % N << endl; } }