N=gets.to_i
E=Array.new(N){[]}
N.times{|n|
    a,b=gets.split.map{|i|i.to_i-1}
    E[a] << [b,n+1]
    E[b] << [a,n+1]
}
Q=[[0,[]]]
C=Array.new(N){false}
max=[]
until Q.empty?
    n,l=Q.shift
    #warn [n,l].inspect
    if C[n]
        m=C[n]&l
        max=(C[n]|l)-m
        break
    end
    C[n]=l
    E[n].each{|nn|
        next if l[-1]==nn[1]
        Q<<[nn[0],l+[nn[1]]]
    }
end
puts max.size
puts max*" "