#include <iostream>
#include <vector>

using namespace std;

const int MAXN = 7001;

vector<vector<int>> adj(MAXN);
vector<pair<int, int>> ans;
bool vis[MAXN];

void dfs(int node) {
	vis[node] = true;
	for (int i = 0; i < adj[node].size(); i++) {
		int newNode = adj[node][i];
		if (!vis[newNode]) {
			dfs(newNode);
			ans.push_back({node, newNode});
		}
	}
}

void solve() {
	dfs(1);
	cout << 2*ans.size()-1 << endl;
	for(int i = 0; i < ans.size(); i++){
        cout << ans[i].first << " " << ans[i].second << endl;
	}
	for(int i = ans.size()-2; i >= 0; i--){
        cout << ans[i].first << " " << ans[i].second << endl;
	}
}

int main() {
	int N, M;
	cin >> N >> M;
	if (N == 1) {
		cout << "0\n";
		return 0;
	}
	for (int i = 0; i < M; i++) {
		int u, v;
		cin >> u >> v;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	solve();
	return 0;
}