rt

#include<iostream>
using namespace std;
int n,m,v,cnt,head[510000],num,u,low[510000],dfn[510000],p[510000],ans,a,b;
struct Edge{
	int to;
	int next;
}edge[1010000];
void add(int u,int v){
	edge[++cnt].to = v;
	edge[cnt].next = head[u];
	head[u] = cnt;
}
void tarjan(int u, int fa, int root){
	low[u] = dfn[u] == ++num;
	for(int i = head[u]; i; i = edge[i].next){
		int v = edge[i].to;
		if(!dfn[v]){
			tarjan(v,u,root);
			low[u] = min(low[u],low[v]);
			if(low[v] >= dfn[u] && dfn[v] <= dfn[b] && u != a){
				p[u] = 1;
			}
		}
		else if(!fa){
				low[u] = min(low[u],dfn[v]);
			}
	}
}
int main(){
	cin>>n;
	cin>>u>>v;
	while(u != 0 && v != 0){
		add(u,v);
		add(v,u);
		cin>>u>>v;
	}
	cin>>a>>b;
	tarjan(a,a,a);
	for(int i = 1; i <= n; i++){
		if(p[i] == 1){
			cout<<i; 
			return 0;
		}
	}
	cout<<"No solution";
	return 0;
}