#include <bits/stdc++.h>
//qwerty47924692
using namespace std;
using ll = long long;
const ll N=1e5+29;
const string br="617283";
#define sz(a)(ll)a.size()
#define f first
#define s second
ll n,pr[N],dp[N][2][2][2][2],root,special;
vector<ll>g[N];
ll get(ll x){
return(x==pr[x] ? x : pr[x]=get(pr[x]));
}ll calc(ll v,ll me,ll up,ll rt,ll sp,ll pr=0){
if(dp[v][me][up][rt][sp]!=-1)return dp[v][me][up][rt][sp];
ll ok=1;
if(v==root&&rt!=me)ok=0;
if(v==special&&sp!=me)ok=0;
if(v==special&&rt&&up)ok=0;
if(!ok)return dp[v][me][up][rt][sp]=1e18;
ll check=0;
if(up)check=1;
if(v==root&&sp)check=1;
if(v==special&&rt)check=1;
ll sum=me;
ll diff=1e18;
for(auto to:g[v]){
if(to==pr)continue;
sum+=calc(to,0,me,rt,sp,v);
diff=min(diff,calc(to,1,me,rt,sp,v)-calc(to,0,me,rt,sp,v));
}
return min((ll)1e18,dp[v][me][up][rt][sp]=(sum+diff*(!check)));
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin>>n;
memset(dp,-1,sizeof(dp));
for(ll i=1;i<=n;i++)pr[i]=i;
for(ll i=1;i<=n;i++){
ll v,u;
cin>>v>>u;
if(get(v)==get(u)){
root=v;
special=u;
continue;
}
pr[get(v)]=get(u);
g[v].push_back(u);
g[u].push_back(v);
}
ll ans=1e18;
for(ll rt=0;rt<2;rt++){
for(ll sp=0;sp<2;sp++){
ans=min(ans,calc(root,rt,0,rt,sp));
}
}
cout<<(ans==1e18 ? -1 : ans);
}
