#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vll vector<ll>
#define len(x) (ll)x.size()
const ll INF = 1e9, INFL = 1e18;
const ll MOD = 1e9 + 7;
const ll maxn = 1e5 + 5;
ll n, m, k = 0;
vll g[maxn];
ll r, sp;
bitset<maxn>vis;
void get_cyc(ll u, ll p = -1){
vis[u] = 1;
for(auto v : g[u]){
if(v == p) continue;
else if(vis[v] == 0) get_cyc(v, u);
else r = v, sp = u;
if(r) return;
}
}
ll dp[maxn][2][2][2][2];
#define dpp dp[u][col_u][col_p][col_r][col_sp]
ll dfs(ll u, ll p, ll col_u, ll col_p, ll col_r, ll col_sp){
if(dpp != -1) return dpp;
if(u == r and col_u != col_r) return dpp = INF;
if(u == sp and col_u != col_sp) return dpp = INF;
if(u == r and col_p and col_sp) return dpp = INF;
if(u == sp and col_p and col_r) return dpp = INF;
dpp = INF;
// eger gorduyu goy qonsu yoxdusa sadece bir dene qonsusunu goy qoya bilerem
ll cm = col_u;
for(auto v : g[u]){
if(v == p) continue;
if((u == r and v == sp) or (u == sp and v == r)) continue;
cm += dfs(v, u, 0, col_u, col_r, col_sp);
}
// cout << u << ' ' << cm << '\n';
if(col_p == 1 or (u == r and col_sp) or (u == sp and col_r)){
// onda uje hec birini goy qoya bilmerem
dpp = min(dpp, cm);
}
else{
// birini goy qoymaliyam
for(auto v : g[u]){
if(v == p) continue;
if((u == r and v == sp) or (u == sp and v == r)) continue;
ll sf = dfs(v, u, 0, col_u, col_r, col_sp);
ll br = dfs(v, u, 1, col_u, col_r, col_sp);
dpp = min(dpp, cm - sf + br);
}
}
return dpp;
}
void _() {
// n dene node var deye bir dene cycle var
// bu cycle-i nezere alib dp yaza bilerik
cin >> n;
for(ll i = 1, x, y; i <= n; i ++){
cin >> x >> y;
g[x].push_back(y);
g[y].push_back(x);
}
ll leaf = -1;
for(ll i = 1; i <= n; i ++) if(len(g[i]) == 1){ leaf = i; break; }
if(leaf == -1){
cout << (n % 4 == 0 ? n / 2 : -1) << '\n';
return;
}
get_cyc(1);
// dp[u][col_u][col_p][col_r][col_sp]
// u node-u, onun coloru, parentin coloru, root-un coloru, special node-un coloru
memset(dp, -1, sizeof(dp));
ll cv = INF;
for(ll col_r : {0, 1}) for(ll col_sp : {0, 1}){
cv = min(cv, dfs(r, -1, col_r, 0, col_r, col_sp));
}
cout << (cv == INF ? -1 : cv) << '\n';
}
signed main() {
cin.tie(0)->sync_with_stdio(0);
ll t = 1;
// cin >> t;
while(t --) _();
}
