#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<ll, ll>
#define fi first
#define sec second
#define ld long double
const int MAXN = 1e5;
const ll INF = 1e18;
const int MOD = 1e9 + 7;
vector<ll> v, adj[MAXN + 5];
ll dp[MAXN + 5][4], dp2[MAXN + 5][4][4];
ll vis[MAXN + 5], is_cycle[MAXN + 5], p[MAXN + 5];
ll st, en;
void dfs(ll idx, ll par){
vis[idx] = 1;
for(auto i : adj[idx]){
if(i == par) continue;
if(vis[i] == 1){
ll st = idx, en = i;
for(;st != en;){
v.push_back(st);
is_cycle[st] = 1;
st = p[st];
}
v.push_back(en);
is_cycle[en] = 1;
}
else if(!vis[i]){
p[i] = idx;
dfs(i, idx);
}
}
vis[idx] = 2;
}
void dfs2(ll idx, ll par){
bool is_leaf = 1;
for(auto i : adj[idx]){
if(i != par && !is_cycle[i]){
dfs2(i, idx);
is_leaf = 0;
for(int j = 0; j < 4; j++){
dp[idx][(j + 1) % 4] = min(dp[idx][(j + 1) % 4], dp[i][j] + ((j + 1) % 4 <= 1));
}
}
}
if(is_leaf){
dp[idx][3] = 0, dp[idx][0] = 1;
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
int tc = 1;
// cin >> tc;
for(;tc--;){
ll N; cin >> N;
for(int i = 1; i <= N; i++){
ll u, v; cin >> u >> v;
adj[u].push_back(v), adj[v].push_back(u);
}
dfs(1, -1);
for(int i = 1; i <= N; i++){
for(int j = 0; j < 4; j++){
dp[i][j] = 4LL * INF;
}
}
for(int i = 1; i <= N; i++){
if(is_cycle[i]){
dfs2(i, -1);
}
}
ll M = (int)v.size() - 1;
for(int i = 0; i <= M; i++){
for(int j = 0; j < 4; j++){
for(int k = 0; k < 4; k++) dp2[i][j][k] = INF;
}
}
for(int i = 0; i < 4; i++) dp2[0][i][i] = dp[v[0]][i];
for(int i = 1; i <= M; i++){
for(int j = 0; j < 4; j++){
// 0 -> biru belum ada pasangan
// 1 -> biru sudah ada pasangan
// 2 -> putih sudah ada pasangan
// 3 -> putih belum ada pasangan
dp2[i][j][0] = min({dp2[i][j][0], dp2[i - 1][j][3] + dp[v[i]][0]});
dp2[i][j][1] = min({dp2[i][j][1], dp2[i - 1][j][3] + dp[v[i]][1], dp2[i - 1][j][0] + dp[v[i]][0]});
dp2[i][j][2] = min({dp2[i][j][2], dp2[i - 1][j][2] + dp[v[i]][2], dp2[i - 1][j][1] + dp[v[i]][3]});
dp2[i][j][3] = min({dp2[i][j][3], dp2[i - 1][j][2] + dp[v[i]][3]});
}
}
ll ans = min({dp2[M][0][3], dp2[M][1][3], dp2[M][2][2], dp2[M][3][2], dp2[M][0][0], dp2[M][1][0]});
vector<ll> x;
for(int i = 1; i <= M; i++) x.push_back(v[i]);
x.push_back(v[0]);
v.swap(x);
for(int i = 0; i <= M; i++){
for(int j = 0; j < 4; j++){
for(int k = 0; k < 4; k++) dp2[i][j][k] = INF;
}
}
for(int i = 0; i < 4; i++) dp2[0][i][i] = dp[v[0]][i];
for(int i = 1; i <= M; i++){
for(int j = 0; j < 4; j++){
// 0 -> biru belum ada pasangan
// 1 -> biru sudah ada pasangan
// 2 -> putih sudah ada pasangan
// 3 -> putih belum ada pasangan
dp2[i][j][0] = min({dp2[i][j][0], dp2[i - 1][j][3] + dp[v[i]][0]});
dp2[i][j][1] = min({dp2[i][j][1], dp2[i - 1][j][3] + dp[v[i]][1], dp2[i - 1][j][0] + dp[v[i]][0]});
dp2[i][j][2] = min({dp2[i][j][2], dp2[i - 1][j][2] + dp[v[i]][2], dp2[i - 1][j][1] + dp[v[i]][3]});
dp2[i][j][3] = min({dp2[i][j][3], dp2[i - 1][j][2] + dp[v[i]][3]});
}
}
// cout << dp2[M][3][1] << "\n";
ans = min({ans, dp2[M][0][3], dp2[M][1][3], dp2[M][2][2], dp2[M][3][2], dp2[M][0][0], dp2[M][1][0]});
if(ans >= INF) ans = -1;
cout << ans << "\n";
}
}
/*
*/
