#include <bits/stdc++.h>
#define MAX (200000 + 7)
#define add push_back
using namespace std;
int f1,f2;
int T,N,M,K,cnt,ans1,c[MAX],LOW[MAX],DFN[MAX],ans2;
int ans=10000;
int root=0;
vector <int> g[MAX],DCC[MAX]; 
stack <int> S;
void init()
{
	while(S.size()) S.pop();
	for(int i=0;i<MAX;i++)
	{
		g[i].clear();
		DCC[i].clear();
		root=0;cnt=0;
		DFN[i]=0;LOW[i]=0;c[i]=0;
	}
}
void Tarjan(int x)
{
	int fa = 0; S.push(x);
	LOW[x] = DFN[x] = ++cnt;
	for (int p = 0; p < g[x].size(); p++)
	{
		const int y = g[x][p];
		if (!DFN[y])
		{
			Tarjan(y);
			LOW[x] = min(LOW[x], LOW[y]);
			if(x==root) fa++;
			if (LOW[y] >= DFN[x])
			{
				K++;
				if(x!=root) c[x]=1; 
				DCC[K].push_back(x);
				if(x==f1) ans1++;
				if(x==f2) ans2++;
				int z = 0;
				do{
					z = S.top(); S.pop();
					if(z==f1) ans1++;
				    if(z==f2) ans2++;
					DCC[K].add(z);
				}while (z != y);
				if(ans1+ans2==1&&x!=f1&&x!=f2) ans=min(ans,x);
			}
		}
		else LOW[x] = min(LOW[x], DFN[y]);
	}
}

int main()
{
	int n;
	cin>>n;
	int u,v;
	while(cin>>u>>v,u,v)
	{
		g[u].push_back(v);
		g[v].push_back(u);
	}
	cin>>f1>>f2;
	for(int i=1;i<=n;i++)
	{
		if(DFN[i]==0)
		{
			root=i;
			Tarjan(i);
		}
	}
	if(ans==10000) cout<<"No solution";
	else cout<<ans;
	return 0;
}