This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <iostream>
#include <vector>
#include <set>
#include <map>
#include <algorithm>
#include <string>
#include <sstream>
#include <fstream>
#include <cmath>
#include <queue>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <bitset>
#include <bits/stdc++.h>
#define lcm(a,b) (a/__gcd(a,b))*b
#define jumanji ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define pb push_back
#define F first
#define S second
#define int long long
#define vi vector<int>
#define ll long long
using namespace std;
vector<vi>G;
//fin endpoints of one edge in a cycle of an undirected graph
int A,B;
const int tam=1e5+100;
const int INF=1e9;
int dp[tam][2][2][2][2];
int padre[tam];
int f(int nodo, int c,int cP, int cA, int cB){
if(dp[nodo][c][cP][cA][cB] != -1) return dp[nodo][c][cP][cA][cB];
if(nodo==A && c!=cA)return dp[nodo][c][cP][cA][cB]=INF;
if(nodo==B && c!=cB)return dp[nodo][c][cP][cA][cB]=INF;
if(nodo==B && cA && cP)return dp[nodo][c][cP][cA][cB]=INF;
bool ok=0;
if(cP)ok=1;
if(nodo==A && cB)ok=1;
if(nodo==B && cA)ok=1;
int sum=c;
for(auto v:G[nodo]){
if(v==padre[nodo])continue;
sum+=f(v,0,c,cA,cB);
}
dp[nodo][c][cP][cA][cB]=INF;
if(ok){
dp[nodo][c][cP][cA][cB]=sum;
}else{
for(auto v:G[nodo]){
if(v==padre[nodo])continue;
dp[nodo][c][cP][cA][cB]=min(dp[nodo][c][cP][cA][cB],sum-f(v,0,c,cA,cB)+f(v,1,c,cA,cB));
}
}
return dp[nodo][c][cP][cA][cB];
}
//union find
int p[tam];
int _find(int x){
if(x==p[x])return x;
return p[x]=_find(p[x]);
}
void join(int x, int y){
x=_find(x);
y=_find(y);
p[x]=y;
}
void dfs(int nodo, int p){
padre[nodo]=p;
for(auto v:G[nodo]){
if(v==p)continue;
dfs(v,nodo);
}
}
signed main(){
jumanji
memset(dp,-1,sizeof dp);
int n,a,b;
cin>>n;
for(int i=0;i<=n;i++)p[i]=i;
vector<pair<int,int>>edges;
G.resize(n+1);
for(int i=0;i<=n;i++){
cin>>a>>b;
if(_find(a)==_find(b)){
A=a;
B=b;
}else{
join(a,b);
G[a].pb(b);
G[b].pb(a);
}
}
dfs(A,-1);
ll res=INF;
res=min(res,f(A,0,0,0,0));
res=min(res,f(A,0,0,0,1));
res=min(res,f(A,1,0,1,0));
res=min(res,f(A,1,0,1,1));
if(res>=INF)cout<<-1<<endl;
else cout<<res<<endl;
return 0;
}
//Guess i wont be comming to church on sunday
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