#include<cstdio>#include<iostream>#include<algorithm>#include<cstring>#include<cmath>#include<vector>#include<queue>#include<map>#include<set>#include<stack>#include<cstdlib>#define INF 100000000#define fi first#define se secondusing namespace std;typedef long long LL;typedef pair<int,int> pii;vector<int> G[1005];int pre[1005],d[1005],ans[1005],tot=0;bool vis[1005];int main(){ int n,k,a,b,i; cin>>n>>k; for(i=1;i<=n;i++) { scanf("%d%d",&a,&b); G[a].push_back(b); } pre[1]=0; d[1]=1; queue<int> q; q.push(1); vis[1]=1; int x,len,v; while(!q.empty()) { x=q.front(); q.pop(); len=G[x].size(); for(i=0;i<len;i++) { v=G[x][i]; if(!vis[v]) { q.push(v); pre[v]=x; d[v]=d[x]+1; vis[v]=1; if(v==k) break; } } if(vis[k]) break; } if(!vis[k]) printf("-1n"); else { printf("%dn",d[k]); for(i=k;i;i=pre[i]) ans[++tot]=i; reverse(ans+1,ans+1+tot); for(i=1;i<=tot;i++) printf("%dn",ans[i]); } return 0;}
