#include <bits/stdc++.h>

using namespace std;

int a[101][101], n, nrc, viz[101], x[101];

ifstream fin ("componenteconexe1.in");
ofstream fout ("componenteconexe1.out");

void Citire()
{
    int i, j;
    fin >> n;
    while (fin >> i >> j)
        a[i][j] = a[j][i] = 1;
    fin.close();
}

void DFS(int k)
{
    viz[k] = 1;
    for (int i = 1; i <= n; i++)
        if (!viz[i] && a[k][i])
            DFS(i);
}


void Rezolvare()
{
    DFS(1);
    int i, nr = 0;
    for (i = 2; i <= n; i++)
        if (!viz[i])
    {
        nr++;
        x[i] = i;
        DFS(i);
    }
    fout << nr << "\n";
    for (i = 1; i <= n; i++)
        if (x[i] == i) fout << "1 " << x[i] << "\n";
}

int main()
{
    Citire();
    Rezolvare();
    return 0;
}