#include<bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define int long long
#define vi vector<int>
#define vvi vector<vector<int>>
#define pii pair<int, int>
#define vpii vector<pair<int, int>>
#define vc vector<char>
#define vb vector<bool>
#define mii map<int,int>
#define f0r(i,n) for(int i=0;i<n;i++)
#define FOR(i,k,n) for(int i=k;i<n;i++)
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define in(a) int a; cin>>a
#define in2(a,b) int a,b; cin>>a>>b
#define in3(a,b,c) int a,b,c; cin>>a>>b>>c
#define in4(a,b,c,d) int a,b,c,d; cin>>a>>b>>c>>d
#define vin(v,n); vi v(n); f0r(i,n){cin>>v[i];}
#define out(a) cout<<a<<'\n'
#define out2(a,b) cout<<a<<' '<<b<<'\n'
#define out3(a,b,c) cout<<a<<' '<<b<<' '<<c<<'\n'
#define out4(a,b,c,d) cout<<a<<' '<<b<<' '<<c<<' '<<d<<'\n'
#define pout(a) cout<<a.first<<' '<<a.second<<'\n'
#define vout(v) for(auto u : v){cout<<u<<' ';} cout<<endl
#define dout(a) cout<<a<<' '<<#a<<endl
#define dout2(a,b) cout<<a<<' '<<#a<<' '<<b<<' '<<#b<<endl
#define yn(x); if(x){cout<<"YES"<<'\n';}else{cout<<"NO"<<'\n';}
const int leg = 1e9 + 7;
const int mod = 998244353;
using namespace std;
const int mxn = 1e5 + 5;
const int ch = 0;
const int pa = 1;
const int L = 0, R = 1;
vvi adj(mxn);
vb vis(mxn);
vi cycle;
vi par(mxn, -1);
vb incyc(mxn);
int dp[mxn][2][2], f[mxn][2][2];
void dfs(int node, int from){
vis[node] = 1;
if(!cycle.empty())return;
for(auto u : adj[node]){
if(u == from)continue;
if(vis[u]){
int cur = node;
while(1){
cycle.pb(cur);
if(cur == u)break;
cur = par[cur];
}
}
else{
par[u] = node;
dfs(u, node);
}
if(!cycle.empty())return;
}
}
void add(int &a, int &b){
if(a == -1)return;
if(b == -1)a = -1;
else a += b;
}
void solve(int node, int from){
int deg = 0;
for(auto u : adj[node]){
if(incyc[u] || u == from)continue;
solve(u, node); deg++;
}
if(deg == 1){
dp[node][0][pa] = 0;
dp[node][1][pa] = 1;
}
f0r(i, 2)f0r(j, 2)dp[node][i][j] = i;
int cant = 0, sum = 0;
int autis = -1;
for(auto u : adj[node]){
if(incyc[u] || u == from)continue;
add(dp[node][0][pa], dp[u][0][ch]);
add(dp[node][1][pa], dp[u][0][pa]);
if(dp[u][0][ch] == -1)cant++, autis = u;
else sum += dp[u][0][ch];
}
if(cant == 0){
int mx = 1e9;
for(auto u : adj[node]){
if(incyc[u] || u == from)continue;
if(dp[u][1][ch] != -1){
mx = min(mx, sum - dp[u][0][ch] + dp[u][1][ch]);
}
}
if(mx == 1e9)dp[node][0][ch] = -1;
else dp[node][0][ch] += mx;
}
else if(cant == 1){
if(dp[autis][1][ch] != -1){
dp[node][0][ch] += sum + dp[autis][1][ch];
}
else dp[node][0][ch] = -1;
}
else{
dp[node][0][ch] = -1;
}
cant = 0, sum = 0;
autis = -1;
for(auto u : adj[node]){
if(incyc[u] || u == from)continue;
if(dp[u][0][pa] == -1)cant++, autis = u;
else sum += dp[u][0][pa];
}
if(cant == 0){
int mx = 1e9;
for(auto u : adj[node]){
if(incyc[u] || u == from)continue;
if(dp[u][1][pa] != -1){
mx = min(mx, sum - dp[u][0][pa] + dp[u][1][pa]);
}
}
if(mx == 1e9)dp[node][1][ch] = -1;
else dp[node][1][ch] += mx;
}
else if(cant == 1){
if(dp[autis][1][pa] != -1){
dp[node][1][ch] += sum + dp[autis][1][pa];
}
else dp[node][1][ch] = -1;
}
else{
dp[node][1][ch] = -1;
}
}
signed main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
//ifstream cin(".in");
//ofstream cout(".out");
in(n);
f0r(i, n){
f0r(j, 2)f0r(k, 2)dp[i][j][k] = -1;
}
f0r(i,n){
in2(a,b); a--; b--;
adj[a].pb(b); adj[b].pb(a);
}
dfs(0, -1);
reverse(all(cycle));
for(auto u : cycle)incyc[u] = 1;
for(auto u : cycle){
solve(u, -1);
}
// f0r(i, cycle.size()){
// cout<<cycle[i]<<' ';
// }
// cout<<'\n';
f0r(i, cycle.size())f0r(j,2)f0r(k,2){
f[i][j][k] = dp[cycle[i]][j][k];
}
//f[root][colour of self][number of coloured neighbours]
int ans = 1e9;
f0r(si, 2)f0r(sj, 2)f0r(sk, 2)if(!(sj == 0 && sk == R) && f[0][si][sj] != -1){
int g[cycle.size()][2][2][2];
f0r(i, 2)f0r(j, 2)f0r(k, 2){
g[0][i][j][k] = -1;
}
g[0][si][sj][sk] = f[0][si][sj];
// out3(si,sj,sk);
// out(f[0][si][sj]);
FOR(v, 1, cycle.size()){
f0r(i, 2)f0r(j,2)f0r(k,2)if(!(j == 0 && k == R)){
g[v][i][j][k] = f[v][i][j];
int mn = 1e9;
if(g[v][i][j][k] != -1){
if(i == 0 && j == 1 && k == L){
if(g[v-1][1][1][L] != -1){
mn = min(mn, g[v-1][1][1][L]);
}
if(g[v-1][1][0][L] != -1){
mn = min(mn, g[v-1][1][0][L]);
}
if(mn != 1e9)g[v][i][j][k] += mn;
else g[v][i][j][k] = -1;
}
else if(i == 0 && j == 1 && k == R){
if(g[v-1][0][1][L] != -1){
mn = min(mn, g[v-1][0][1][L]);
}
if(g[v-1][0][0][L] != -1){
mn = min(mn, g[v-1][0][0][L]);
}
if(mn != 1e9)g[v][i][j][k] += mn;
else g[v][i][j][k] = -1;
}
else if(i == 1 && j == 1 && k == L){
if(g[v-1][1][1][R] != -1){
mn = min(mn, g[v-1][1][1][R]);
}
if(mn != 1e9)g[v][i][j][k] += mn;
else g[v][i][j][k] = -1;
}
else if(i == 1 && j == 1 && k == R){
if(g[v-1][0][1][R] != -1){
mn = min(mn, g[v-1][0][1][R]);
}
if(mn != 1e9)g[v][i][j][k] += mn;
else g[v][i][j][k] = -1;
}
else if(i == 0 && j == 0){
if(g[v-1][0][1][L] != -1){
mn = min(mn, g[v-1][0][1][L]);
}
if(g[v-1][0][0][L] != -1){
mn = min(mn, g[v-1][0][0][L]);
}
if(mn != 1e9)g[v][i][j][k] += mn;
else g[v][i][j][k] = -1;
}
else{
if(g[v-1][0][1][R] != -1){
mn = min(mn, g[v-1][0][1][R]);
}
if(mn != 1e9)g[v][i][j][k] += mn;
else g[v][i][j][k] = -1;
}
}
}
}
tuple<int,int,int>t = {si,sj,sk};
/*
if(t == mt(1,1,R)){
// dout(g[1][1][1][L]);
f0r(i,cycle.size())f0r(j, 2)f0r(k,2)f0r(l,2){
if(g[i][j][k][l] == 0)out4(i,j,k,l);
}
}
*/
f0r(i, 2)f0r(j,2)f0r(k,2)if(!(j == 0 && k == R)){
tuple<int,int,int>s = {i,j,k};
if(s == mt(0,1,L)){
if(t == mt(0,1,R) || t == mt(0,0,L))if(g[cycle.size() - 1][i][j][k] != -1){
ans = min(ans, g[cycle.size() - 1][i][j][k]);
}
}
else if(s == mt(0,1,R)){
if(t == mt(1,1,R) || t == mt(1,0,L))if(g[cycle.size() - 1][i][j][k] != -1){
// out("HERE");
// dout(g[cycle.size() - 1][i][j][k]);
// dout2(si,sj);
ans = min(ans, g[cycle.size() - 1][i][j][k]);
}
}
else if(s == mt(1,1,L)){
if(t == mt(0,1,L))if(g[cycle.size() - 1][i][j][k] != -1){
ans = min(ans, g[cycle.size() - 1][i][j][k]);
}
}
else if(s == mt(1,1,R)){
if(t == mt(1,1,L))if(g[cycle.size() - 1][i][j][k] != -1){
ans = min(ans, g[cycle.size() - 1][i][j][k]);
}
}
else if(s == mt(0,0,L)){
if(t == mt(0,0,L) || t == mt(0,1,R))if(g[cycle.size() - 1][i][j][k] != -1){
ans = min(ans, g[cycle.size() - 1][i][j][k]);
}
}
else{
if(t == mt(0,1,L))if(g[cycle.size() - 1][i][j][k] != -1){
ans = min(ans, g[cycle.size() - 1][i][j][k]);
}
}
}
}
if(ans == 1e9)out(-1);
else out(ans);
}
