#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("izolate.in");
ofstream fout("izolate.out");
int n , a[105][105], g[105];
int main()
{
int i , j;
fin >> n;
while(fin >> i >> j)
{
a[i][j] = a[j][i] = 1;
}
for(int i = 1 ; i <= n ; i++){
g[i] = 0;
for(int j = 1; j <= n ; ++j)
if(a[i][j] == 1)
g[i] ++;
}
int nrv = 0;
for(int i = 1 ; i <= n ; i++)
if(g[i] == 0)
nrv ++;
fout << nrv << " ";
for(int i = 1 ; i <= n ; i++)
if(g[i] == 0)
fout << i << " ";
return 0;
}