#include "bits/stdc++.h"
// @JASPER'S BOILERPLATE
using namespace std;
using ll = long long;
#ifdef JASPER
#include "debug.h"
#else
#define debug(...) 166
#endif
#define int long long
struct DisJointSet {
int n;
vector <int> pa, sz;
DisJointSet(int _n) {
n = _n;
pa.resize(n + 5);
sz.resize(n + 5);
for (int i = 1; i <= n; ++i) {
pa[i] = i;
sz[i] = 1;
}
}
int get(int u) { return (u == pa[u]? u : pa[u] = get(pa[u])); }
bool unite(int u, int v) {
u = get(u);
v = get(v);
if (u == v) return 0;
if (sz[u] < sz[v]) swap(u, v);
sz[u] += sz[v];
pa[v] = u;
return 1;
}
};
const int N = 1e5 + 5;
const int INF = 1e9;
vector <int> adj[N];
int st, en;
int ans;
int dp[N][2][2][2][2];
// dp(x, self, pa, root, end) :
// number of 1 nodes in x's subtree with color self, color of parent self, color of root, color of other root: end
int dfs(int u, int p, bool self, bool pa, bool root, bool end) {
if (dp[u][self][pa][root][end] != -1)
return dp[u][self][pa][root][end];
// invalid case
bool invalid = false;
if (u == st && root != self) invalid = true;
if (u == en && end != self) invalid = true;
if (u == en && pa == 1 && root == 1) invalid = true;
if (invalid)
return dp[u][self][pa][root][end] = INF;
int res = INF;
bool must = false; // handle case when current node having adjacent one 1-node
if (pa) must = true;
if (u == st && end == 1) must = true;
if (u == en && root == 1) must = true;
int sum = 0;
if (self) ++sum;
// must = 1 -> u only takes result from 0-node child
for (int v : adj[u]) {
if (v == p) continue;
sum += dfs(v, u, 0, self, root, end);
}
if (must)
res = min(res, sum);
// must = 0 -> fix one child by 1, others by 0
if (!must) {
for (int v : adj[u]) {
if (v == p) continue;
int cur = sum - dfs(v, u, 0, self, root, end) + dfs(v, u, 1, self, root, end);
res = min(res, cur);
}
}
if (res > INF) res = INF;
return dp[u][self][pa][root][end] = res;
}
signed main() {
cin.tie(0) -> sync_with_stdio(0);
#ifdef JASPER
freopen("in1", "r", stdin);
#endif
int n; cin >> n;
DisJointSet dsu(n);
for (int i = 1; i <= n; ++i) {
int u, v;
cin >> u >> v;
if (!dsu.unite(u, v)) {
st = u;
en = v;
}
else {
adj[u].push_back(v);
adj[v].push_back(u);
}
}
if (st > en) swap(st, en);
debug(st, en);
ans = INF;
for (int i = 0; i <= 1; ++i) {
for (int j = 0; j <= 1; ++j) {
memset(dp, -1, sizeof dp);
ans = min(ans, dfs(st, 0, i, 0, i, j));
}
}
if (ans == INF) ans = -1;
cout << ans << "\n";
return 0;
}
