#include <bits/stdc++.h>
#define int long long
using namespace std;
const int nmax = 1e5 + 1;
int grad[nmax];
bool f[nmax];
int32_t main() {
int n;
cin >> n;
for (int i = 1; i <= n; i++) {
int a, b;
cin >> a >> b;
grad[a]++, grad[b]++;
}
vector<int> lf;
int root = -1;
for (int i = 0; i <= n; i++) {
if (grad[i] == 1) {
lf.push_back(i);
} else {
assert(grad[i] == n);
root = i;
}
}
if (lf.size() == n + 1) {
assert(n == 1);
root = 1;
lf.pop_back();
}
cout << (1 << (n - 1)) << '\n';
for (int i = 0; i < (1 << n); i++) {
if (!f[i]) {
f[i] = 1;
vector<int> ord(n + 1);
ord[root] = i;
for (int bit = 0; bit < n; bit++) {
// sa ramana doar bit ul bit
int xr = (i ^ (1 << bit));
ord[lf[bit]] = xr;
f[xr] = 1;
}
for (auto it : ord) {
cout << it << " ";
}
cout << '\n';
}
}
return 0;
}
