#include <iostream>
#include <stdint.h>
using namespace std;
typedef uint32_t u32;

struct s_connection {
    u32 a;
    u32 b;
};

static bool walked[100000];
static u32 connection_count = 0;
static u32 added_count = 0;
static s_connection connections[200000];
static s_connection added[200000];
static u32 cities, roads;

int main() {

    cin >> cities >> roads;
    for(u32 i = 0; i < roads; i++) {
        u32 a, b;
        cin >> a >> b;
        connections[connection_count++] = {a, b};
    }

    walked[1] = true;
    for(u32 city_i = 1; city_i < cities; city_i++) {
        u32 curr = city_i;
        u32 target = city_i + 1;
        if(walked[target]) {
            continue;
        }

        bool reset_loop = true;
        while(reset_loop) {
            reset_loop = false;
            for(int connection_i = 0; connection_i < (int)connection_count; connection_i++) {
                s_connection c = connections[connection_i];
                if(walked[c.a] && !walked[c.b]) {
                    walked[c.b] = true;
                    reset_loop = true;
                }
                else if(walked[c.b] && !walked[c.a]) {
                    walked[c.a] = true;
                    reset_loop = true;
                }
                if(walked[c.a] && walked[c.b]) {
                    connections[connection_i--] = connections[--connection_count];
                }
                if(walked[target]) { break; }
            }
        }
        if(!walked[target]) {
            connections[connection_count++] = {curr, target};
            added[added_count++] = {curr, target};
            walked[target] = true;
        }
    }

    cout << added_count << endl;
    for(u32 i = 0; i < added_count; i++) {
        cout << added[i].a << " " << added[i].b << endl;
    }
    return 0;
}