#include <stdio.h>
#include<cstring>
#include<fstream>

using namespace std;

	ofstream fo("mesaj4.out");
int n, m,mm, viz[100005];
typedef struct{
int n1,n2;
} afisare;
afisare afis[100005];

typedef struct nod
{
	int x;
	nod *a;
} *pNod;
pNod v[100005];

void add(pNod &dest, int val)
{
	pNod p;
	p = new nod;
	p -> x = val;
	p -> a = dest;
	dest = p;
}

void citire()
{
	freopen("mesaj4.in","r",stdin);
	scanf("%d %d",&n,&m);
	fo<<2*n-2<<"\n";
	int i, x, y;

	for (i = 1; i <= m; i++)
	{
		scanf("%d %d",&x,&y);
		add(v[x], y);
		add(v[y], x);
	}
}

void DFS(int nod,int precedent)
{
	pNod p;
	viz[nod] = 1;

	if(precedent!=0) {afis[++mm].n1=precedent; afis[mm].n2=nod; }
	for (p = v[nod]; p != NULL; p = p -> a) if (!viz[p -> x]) DFS(p -> x,nod);
    if(precedent!=0) fo<<nod<<" "<<precedent<<"\n";
}

int main()
{
	citire();
	int i;
	for (i = 1; i <= n; i++) if (!viz[i]) DFS(i,0);
	memset(viz,0,sizeof(viz));
	for(i=1;i<=mm;i++)
        fo<<afis[i].n1<<" "<<afis[i].n2<<"\n";
        fo.close();


	return 0;
}