#include<bits/stdc++.h>

 using namespace std;

 #define Fopen freopen("_in.txt","r",stdin); freopen("_out.txt","w",stdout);

 #define LL long long

 #define ULL unsigned LL

 #define fi first

 #define se second

 #define pb push_back

 #define lson l,m,rt<<1

 #define rson m+1,r,rt<<1|1

 #define max3(a,b,c) max(a,max(b,c))

 #define min3(a,b,c) min(a,min(b,c))

 typedef pair<int,int> pll;

 const int INF = 0x3f3f3f3f;

 const LL mod = 1e9+;

 const int N = 1e5+;

 vector<int> son[N];

 int ans = ;

 int cnt[N];

 void dfs(int o, int u){

     cnt[u] = ;

     for(int i = ; i < son[u].size(); i++){

         int v = son[u][i];

         if(o == v) continue;

         dfs(u,v);

         cnt[u] += cnt[v];

     }

 }

 void dfs2(int o, int u){

     if(cnt[u]% == ) ans++;

     for(int i = ; i < son[u].size(); i++){

         int v = son[u][i];

         if(o == v) continue;

         dfs2(u,v);

     }

 }

 int main(){

     ///Fopen;

     int n, u, v;

     scanf("%d", &n);

     for(int i = ; i < n; i++){

         scanf("%d%d", &u, &v);

         son[u].pb(v);

         son[v].pb(u);

         cnt[u]++;

         cnt[v]++;

     }

     if(n&){

         printf("-1");

         return ;

     }

     dfs(,);

     for(int i = ; i < son[].size(); i++)

         dfs2(,son[][i]);

     printf("%d", ans);

     return ;

 }