/* Burung ini cuma template
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*/
#include<bits/stdc++.h>
#define mp make_pair
#define fs first
#define sc second
#define pb push_back
#define debug(x) cout<<#x<<" = "<<(x)<<endl
#define mod 1000000007
#define INF 1e9
#define ALPHABET_SIZE 26
using namespace std;
/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( )
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
* if you have no idea just guess the appropriate well-known algo instead of doing nothing :/
*/
vector<int> adj[100005];
int specialNode, root;
long long depe[100005][2][2][2][2];
// the param for DP: now, currentColor (0/1), parentColor (0/1), rootColor (0/1), specialNodeColor (0/1)
// transition:
// - if currentColor = 1 (black)
// - if parentColor = 1 (black), all of the child should 0 (white)
// - if parentColor = 0 (white), choose 1 child that should be black
// - if currentColor = 0 (white)
// - if parentColor = 1 (black), all of the child should 0 (white)
// - if parentColor = 0 (white), choose 1 child that should be black
//
// root is special (its parentColor is the specialNodeColor):
// - if currentColor = 1 (black)
// - if specialNodeColor = 1 (black), all of the child should 0 (white)
// - if specialNodeColor = 0 (white), choose 1 child that should be black
// - if currentColor = 0 (white)
// - if specialNodeColor = 1 (black), all of the child should 0 (white)
// - if specialNodeColor = 0 (white), choose 1 child that should be black
// now == specialNode:
// - if currentColor different from colorSpecialNode, return IMPOSSIBLE
// - if currentColor = 1 (black), rootColor = 1, and parentColor = 1, then return IMPOSSIBLE (this special node sees 2 black)
long long dp(int now, int par, int currentColor, int parentColor, int rootColor, int specialNodeColor) {
if(now == specialNode) {
if(currentColor != specialNodeColor) {
return INF;
}
if(rootColor == 1 && parentColor == 1) {
return INF;
}
}
long long &ret = depe[now][currentColor][parentColor][rootColor][specialNodeColor];
if(ret != -1) return ret;
// count the dp if all of his child is white, store it in whiteCost
long long whiteCost[adj[now].size() + 1];
long long total = 0;
for(int i = 0; i < adj[now].size(); i++) {
if(adj[now][i] == par || (now == root && adj[now][i] == specialNode) || (now == specialNode && adj[now][i] == root)) continue;
whiteCost[i] = dp(adj[now][i], now, 0, currentColor, rootColor, specialNodeColor);
// if(rootColor == 1 && specialNodeColor == 0 && now == 1) {
// cout << "now = " << now << " adj[now][i] = " << adj[now][i] << " rootColor = " << rootColor << " specialNodeColor = " << specialNodeColor << " whiteCost = " << whiteCost[i] << endl;
// }
total += whiteCost[i];
}
// if(now == specialNode) {
// cout << "SPECIAL NODE now = " << now << " currentColor = " << currentColor << " parentColor = " << parentColor << " rootColor = " << rootColor << " specialNodeColor = " << specialNodeColor << endl;
// }
if(parentColor == 1) {
ret = total;
} else {
// if currentColor = 1 (black), parentColor = 0 (white), then we should choose 1 child that should be black
// but if there is no child, we should return IMPOSSIBLE
ret = INF;
for(int i = 0; i < adj[now].size(); i++) {
if(adj[now][i] == par || (now == root && adj[now][i] == specialNode) || (now == specialNode && adj[now][i] == root)) continue;
int cost = 0;
if(currentColor == 1) cost = 2;
// exchange the color of the child[i] from white to black
ret = min(ret, total - whiteCost[i] + dp(adj[now][i], now, 1, currentColor, rootColor, specialNodeColor) + cost);
}
}
return ret;
}
bool vis[100005];
pair<int, int> specialEdge;
void findCycle(int now, int par) {
for(auto nxt : adj[now]) {
if(nxt == par) continue;
if(vis[nxt]) {
specialEdge = {now, nxt};
return;
}
vis[nxt] = true;
findCycle(nxt, now);
}
}
int main(){
int n; cin >> n;
for(int i = 1; i <= n; i++){
int u, v; cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
// we should pick the special edge from the cycle
// we should find the cycle first
memset(vis, false, sizeof(vis));
vis[1] = true;
findCycle(1, -1);
// specialEdge = {root, specialNode}
specialNode = specialEdge.second;
root = specialEdge.first;
// cout << "specialEdge = " << specialEdge.first << " " << specialEdge.second << endl;
// 4 case for the special edge (root, specialNode):
// - both of them are black
// - both of them are white
// - root is black, specialNode is white
// - root is white, specialNode is black
memset(depe, -1, sizeof(depe));
long long ans = INF;
for(int i = 0; i < 2; i++) {
for(int j = 0; j < 2; j++) {
int cost = 0;
if(i == 1 && j == 1) {
cost = 2;
}
ans = min(ans, dp(root, -1, i, j, i, j) + cost);
// cout << "i = " << i << " j = " << j << " dp = " << dp(root, -1, i, j, i, j) + cost << endl;
}
}
if(ans >= INF) {
ans = -1;
}
cout << ans << endl;
}
