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

using namespace std;

int n, m, viz[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);
	freopen("mesaj4.out","w",stdout);
	scanf("%d %d",&n,&m);
	printf("%d\n",2*n-2);
	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;
	for (p = v[nod]; p != NULL; p = p -> a) if (!viz[p -> x]) DFS(p -> x,nod);
    if(precedent!=0) printf("%d %d\n",nod,precedent);
}
void DFS2(int nod,int precedent)
{
	pNod p;
	viz[nod] = 1;
	if(precedent!=0) printf("%d %d\n",nod,precedent);
	for (p = v[nod]; p != NULL; p = p -> a) if (!viz[p -> x]) DFS(p -> x,nod);

}

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 <= n; i++) if (!viz[i]) DFS2(i,0);

	return 0;
}