```#include<bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define openfile ifstream cin; ofstream cout; cin.open("input.txt"); cout.open("output.txt");
#define f(i, x, y) for(int i = x; i < y; i++)
#define all(X) X.begin(), X.end()
#define int long long
#define ll long long
#define key pair<int, int>
#define keyd pair<double, double>
#define ff first
#define ss second
#define double long double
int mod = 1e9+7;
const int inf = 1e18;
using namespace std;

vector<int> g[200001];
int dp[200001][3];

int ans = 0;

void dfs(int s, int p, int lvl)
{
int sum0 = 0, sum1 = 0, sum2 = 0;
for(int i : g[s])
{
if(i == p) continue;
dfs(i, s, lvl+1);
if(lvl < 2) continue;
sum0 += min(dp[i][0], dp[i][1]);
dp[s][1] += min(dp[i][0], min(dp[i][1], dp[i][2]));
dp[s][2] += min(dp[i][0], dp[i][1]);
}

if(lvl < 2 || (lvl == 2 && g[s].size() == 1)) return;
dp[s][0] = inf; dp[s][1]++;

for(int i : g[s])
{
if(i == p) continue;
dp[s][0] = min(dp[s][0], sum0 + max(0ll, dp[i][1] - dp[i][0]));
}

if(lvl == 2)
ans += min(dp[s][0], min(dp[s][1], dp[s][2]));
}

main()
{
memset(dp, 0, sizeof(dp));
int n; cin>>n;
if(n == 1) { cout<<0; return 0; }
f(i, 1, n)
{
int s, d; cin>>s>>d; g[s].pb(d); g[d].pb(s);
}
dfs(1, -1, 0);

//    f(i, 1, n+1) cout<<dp[i][0]<<" "<<dp[i][1]<<" "<<dp[i][2]<<"\n";
cout<<ans;
}```

`3`