#include <iostream>
#include <vector>
#include <stack>

using namespace std;

stack<int> a;

void dfs(int v, vector<vector<int>> &graph, vector<bool> &visited, int &ans) {
    visited[v] = true;
    for (int i = 0; i < (int)graph[v].size(); ++i) {
        if (graph[v][i] && !visited[i]){
            ans++;
            a.push(v+1);
            a.push(i+1);
            dfs(i, graph, visited, ans);
        }
    }
}

int main(){
    int ans=0;
    int n,m;
    cin>>n>>m;
    vector< vector<int> > graph;
    vector<int> visited;

    int a, b;
    for(int i=0;i<m;i++){
        cin>>a>>b;
        graph[a-1][b-1]=true;
        graph[b-1][a-1]=true;
    }

    for(int i=0;i<n;i++){
        if(!visited[i]){
            dsf(i,graph,visited,ans);
        }
    }
    cout<<a<<'\n';
    while(!a.empty()){
        cout<<a.top()<<' ';
        a.pop();
        cout<<a.top()<<'\n';
        a.pop();
    }
}