//Achen
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#include<vector>
#include<cmath>
#include<map>
const int N=1e5+7,mod=998244353,bs=1011139;
typedef long long LL;
using namespace std;
int n,tot,ans=-1;
map<LL,int>mp;
LL power[N],fh[N];template<typename T> void read(T &x) {char ch=getchar(); x=0; T f=1;while(ch!='-'&&(ch<'0'||ch>'9')) ch=getchar();if(ch=='-') f=-1,ch=getchar();for(;ch>='0'&&ch<='9';ch=getchar()) x=x*10+ch-'0'; x*=f;
}int ecnt,fir[N],nxt[N*2],to[N*2],sz[N],ha[N],f[N];
void add(int u,int v) {nxt[++ecnt]=fir[u]; fir[u]=ecnt; to[ecnt]=v;nxt[++ecnt]=fir[v]; fir[v]=ecnt; to[ecnt]=u;
}bool cmp(const int &A,const int &B) { return ha[A]<ha[B]; }vector<int>v[N];
void get_hash(int x) {int up=v[x].size();ha[x]=0;sort(v[x].begin(),v[x].end(),cmp);for(int i=0;i<up;i++) ha[x]=((LL)ha[x]+(LL)ha[v[x][i]]*power[i+1]%mod)%mod;ha[x]=((LL)ha[x]+sz[x])%mod;
}void dfs(int x,int fa) {sz[x]=1; f[x]=fa;for(int i=fir[x];i;i=nxt[i]) if(to[i]!=fa) {dfs(to[i],x);v[x].push_back(to[i]);sz[x]+=sz[to[i]];}get_hash(x);
}int pr[N];
void make_hash(int x) {sort(v[x].begin(),v[x].end(),cmp);int up=v[x].size(); pr[0]=0;for(int i=0;i<up;i++) pr[i+1]=((LL)pr[i]+power[i+1]*ha[v[x][i]])%mod;LL has=0;ha[x]=(pr[up]+tot)%mod;for(int i=up-1;i>=0;i--) {if(v[x][i]!=n+2) {fh[v[x][i]]=((has*power[i]%mod+pr[i])%mod+(tot-sz[v[x][i]]))%mod;if(ecnt==2*n&&!nxt[fir[v[x][i]]]&&mp[fh[v[x][i]]]) if(ans==-1||v[x][i]<ans) ans=v[x][i];} else if(ecnt==2*n&&!nxt[fir[f[x]]]) {LL tpp=((has*power[i]%mod+pr[i])%mod+(tot-1))%mod;if(mp[tpp]) if(ans==-1|f[x]<ans) ans=f[x];}has=(has+ha[v[x][i]])*bs%mod;}
}void dp(int x,int fa) {if(fa) { ha[n+2]=fh[x]; v[x].push_back(n+2); }make_hash(x);for(int i=fir[x];i;i=nxt[i]) if(to[i]!=fa) {dp(to[i],x);}
}int main() {read(n); power[0]=1; tot=n;for(int i=1;i<=n;i++) power[i]=power[i-1]*bs%mod;for(int i=1;i<n;i++) {int u,v; read(u); read(v); add(u,v); }dfs(1,0); dp(1,0);for(int i=1;i<=n;i++) mp[ha[i]]=1,v[i].clear();memset(fir,0,sizeof(fir)); ecnt=0; tot++;for(int i=1;i<=n;i++) {int u,v; read(u); read(v); add(u,v); }dfs(1,0); dp(1,0);printf("%d\n",ans);return 0;
}
/*
5
1 2
2 3
1 4
1 5
1 2
2 3
3 4
4 5
3 6
*/