#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const int N = 100000;
const ll INF = 1000000;
vector <int> graf[N+5];
vector <int> cyc;
bool in_cycle[N+5];
ll dp[N+5][2][2];
ll pd[2][2][2][2];
ll ppd[2][2][2][2];
bool visited[N+5];
int pcc;
bool dfs_cycle(int v, int p){
visited[v] = 1;
for(auto c : graf[v]){
if(c == p) continue;
if(visited[c]){
pcc = c;
cyc.push_back(v);
return 1;
}
if(dfs_cycle(c, v)){
if(pcc) cyc.push_back(v);
if(v == pcc) pcc = 0;
return 1;
}
}
return 0;
}
void dfs(int v, int p){
dp[v][0][0] = dp[v][0][1] = dp[v][1][0] = dp[v][1][1] = INF;
vector <int> vec;
for(auto c : graf[v]){
if(in_cycle[c] || c == p) continue;
dfs(c, v);
vec.push_back(c);
}
/// ukljucen, sat
if(!vec.empty()){
dp[v][1][1] = 1;
ll mn = dp[vec[0]][1][0] - dp[vec[0]][0][0];
for(auto c : vec){
dp[v][1][1] += dp[c][0][0];
mn = min(mn, dp[c][1][0] - dp[c][0][0]);
}
dp[v][1][1] += mn;
}
/// ukljucen, nesat
dp[v][1][0] = 1;
for(auto c : vec) dp[v][1][0] += dp[c][0][0];
/// neukljucen, sat
if(!vec.empty()){
dp[v][0][1] = 0;
ll mn = dp[vec[0]][1][1] - dp[vec[0]][0][1];
for(auto c : vec){
dp[v][0][1] += dp[c][0][1];
mn = min(mn, dp[c][1][1] - dp[c][0][1]);
}
dp[v][0][1] += mn;
}
/// neukljucen, nesat
dp[v][0][0] = 0;
for(auto c : vec) dp[v][0][0] += dp[c][0][1];
}
int main(){
ios_base::sync_with_stdio(false), cin.tie(0);
cout.precision(10);
cout << fixed;
int n;
cin >> n;
for(int i=1; i<=n; i++){
int a, b;
cin >> a >> b;
graf[a].push_back(b);
graf[b].push_back(a);
}
if(!dfs_cycle(1, 0)){
return 0;
dfs(1, 0);
ll res = INF;
for(int j=0; j<=1; j++) for(int k=0; k<=1; k++) res = min(res, dp[1][j][k]);
cout << (res >= INF ? -1 : res) << "\n";
return 0;
}
for(auto v : cyc) in_cycle[v] = 1;
for(auto v : cyc) dfs(v, 0);
int x = cyc.back();
cyc.pop_back();
int y = cyc.back();
cyc.pop_back();
for(int a=0; a<=1; a++) for(int b=0; b<=1; b++) for(int c=0; c<=1; c++) for(int d=0; d<=1; d++) pd[a][b][c][d] = INF;
for(int a=0; a<=1; a++) for(int b=0; b<=1; b++) for(int c=0; c<=1; c++) for(int d=0; d<=1; d++){
if(a && d){
continue;
}
if(c && b){
continue;
}
pd[a][b | c][c][d | a] = min(pd[a][b |c][c][d | a], dp[x][a][b] + dp[y][c][d]);
}
reverse(cyc.begin(), cyc.end());
for(auto v : cyc){
for(int a=0; a<=1; a++) for(int b=0; b<=1; b++) for(int c=0; c<=1; c++) for(int d=0; d<=1; d++) ppd[a][b][c][d] = pd[a][b][c][d], pd[a][b][c][d] = INF;
for(int a=0; a<=1; a++) for(int b=0; b<=1; b++) for(int c=0; c<=1; c++) for(int d=0; d<=1; d++){
for(int e=0; e<=1; e++){
for(int f=0; f<=1; f++){
if(a && d) continue;
if(b && c) continue;
if(!b && !c) continue;
pd[e][f][c][d | a] = min(pd[e][f][c][d | a], ppd[e][f][a][b] + dp[v][c][d]);
}
}
}
}
ll res = INF;
for(int a=0; a<=1; a++) for(int b=0; b<=1; b++) for(int c=0; c<=1; c++) for(int d=0; d<=1; d++){
if(a && d) continue;
if(b && c) continue;
if(!a && !d) continue;
if(!b && !c) continue;
res = min(res, pd[a][b][c][d]);
}
cout << (res >= INF ? -1 : res) << "\n";
return 0;
}
