CicluL

#include <iostream>
#include <fstream>
#include <cassert>

using namespace std;

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

int n , A[21][21], L , x[21], uz[21], gasit = false;

bool OK(int k)
{
    if(k == 1)
        return true;
    if(A[x[k-1]][x[k]] == 0)
        return false;
    return true;
}

void Back(int k)
{
    for(int i = 1; i <= n && ! gasit; i ++)
        if(uz[i] == 0)
        {
            uz[i] = 1;
            x[k] = i;
            if(OK(k))
            {
                if(k == L)
                {
                    if(A[x[k]][x[1]] == 1)
                    {
                        for(int i = 1; i <= k ; i ++)
                            fout << x[i] << " ";
                        fout << x[1] << '\n';
                        gasit = true;
                    }
                }
                else
                    Back(k + 1);
            }
            uz[i] = 0;
        }
}

int main()
{
    int i , j, m;
    fin >> n >> m;
    while(m > 0)
    {
        fin >> i >> j;
        if(A[i][j] == 1)
            cout << i << " " << j << endl;;
        A[i][j] = A[j][i] = 1;
        m --;
    }
    fin >> L;
    Back(1);
    return 0;
}