#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5+5;
vector<int> adj[MAXN];
int marc[MAXN], pai[MAXN], b[2], v[2];
int dp[2][2][MAXN];
void dfs(int s){
marc[s] = 1;
for(int viz : adj[s]){
if(viz == pai[s])continue;
if(marc[viz]){
if(b[0] == 0){
b[0] = viz;
b[1] = s;
}
continue;
}
pai[viz] = s;
dfs(viz);
}
}
void fazdp(int i){ // dp c p i
marc[i] = 1;
dp[0][1][i] = 0; dp[1][1][i] = 1;
for(int viz : adj[i])
if(pai[viz] == i){
fazdp(viz);
dp[0][1][i] += dp[0][0][viz];
dp[1][1][i] += dp[0][1][viz];
}
dp[0][0][i] = MAXN; dp[1][0][i] = MAXN;
for(int viz : adj[i])
if(pai[viz] == i){
dp[0][0][i] = min(dp[0][0][i], dp[1][0][viz] + dp[0][1][i] - dp[0][0][viz]);
dp[1][0][i] = min(dp[0][0][i], dp[1][1][viz] + dp[1][1][i] - dp[0][1][viz]);
}
for(int x = 0; x < 2; x++)
if(b[x] == i){
if( v[x^1] == 1){
dp[0][0][i] = dp[0][1][i];
dp[1][0][i] = dp[1][1][i];
dp[0][1][i] = MAXN;
dp[1][1][i] = MAXN;
}
dp[ v[x]^1 ][0][i] = MAXN; dp[ v[x]^1 ][1][i] = MAXN;
}
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n; cin>>n;
for(int i = 1; i <= n; i++){
int a,b; cin>>a>>b;
adj[a].push_back(b);
adj[b].push_back(a);
}
dfs(1);
int ans = MAXN;
for(int mask = 0; mask < 4; mask++){
for(int i = 0; i < 2; i++)v[i] = ((mask & (1<<i)) > 0);
fazdp(1);
ans = min({ans, dp[0][0][1], dp[1][0][1]});
}
if(ans == MAXN)cout<<"-1\n";
else cout<<ans<<"\n";
}
