#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define pll ll
#define ld long double
#define el cout << '\n'
#define f1(i,n) for(ll i=1;i<=n;i++)
#define __file_name ""
using namespace std;
using namespace __gnu_pbds;
#define ordered_set tree<pll, null_type, less<pll>, rb_tree_tag, tree_order_statistics_node_update>
using namespace std;
const ll maxn = 4e5+5, inf=1e18;
/*
// Be yeu tle roi cay qua
ll dfs(ll u, ll p){
if(a[u]){
// cout << u << ' ' << a[u];el;
values[u].insert(a[u]);
return 0;
}
ll resp = 0;
ll le = 0, ri = 0;
for(ll c: G[u]){
if(c != p){
resp += dfs(c, u);
if(le == 0) le = c;
else ri = c;
}
}
if(values[ri].size() < values[le].size()) swap(values[ri], values[le]);
// le < ri
ll res1 = 0, res2 = 0;
// res1: count inversion if le comes before ri
// res2: count inversions if le comes after ri
for(auto item: values[le]){
res1 += values[ri].order_of_key(item);
res2 += values[ri].size() - values[ri].order_of_key(item+1);
}
// cout << u << ' ' << res1 << ' ' << res2;el;
for(ll c: G[u]){
if(c != p){
if(values[c].size() > values[u].size()) values[u].swap(values[c]);
for(auto item: values[c]){
values[u].insert(item);
}
values[c].clear();
}
}
return resp + min(res1, res2);
}
*/
ll n,a[maxn],sz[maxn];
pair<ll,ll> bit[maxn];
vector<ll> G[maxn];
vector<ll> sus;
void update(ll idx, pair<ll,ll> v){
while(idx <= n){
bit[idx].first += v.first;
bit[idx].second += v.second;
idx += idx & (-idx);
}
}
pair<ll,ll> getSum(ll idx){
// {sum, count}
pair<ll,ll> res = {0ll, 0ll};
while(idx > 0){
res.first += bit[idx].first;
res.second += bit[idx].second;
idx -= idx & (-idx);
}
return res;
}
void dfs_size(ll u, ll p){
sz[u] = 1;
for(ll c: G[u]){
if(c != p){
dfs_size(c, u);
sz[u] += sz[c];
}
}
}
void delete_(ll u, ll p){
if(a[u]){
update(a[u], {-1ll, -1ll});
return;
}
for(ll c: G[u]){
if(c != p){
delete_(c, u);
}
}
}
void add_(ll u, ll p){
if(a[u]){
update(a[u], {1ll , 1ll});
return;
}
// update(order[u], {c[u], 1ll});
for(ll c: G[u]){
if(c != p){
add_(c, u);
}
}
}
ll dfslow(ll u, ll p){
if(a[u]){
return getSum(a[u] - 1).first;
}
ll res = 0;
for(ll c: G[u]){
if(c != p){
res += dfslow(c, u);
}
}
return res;
}
ll dfshigh(ll u, ll p){
if(a[u]){
return getSum(n).first - getSum(a[u]).first;
}
ll res = 0;
for(ll c: G[u]){
if(c != p){
res += dfshigh(c, u);
}
}
return res;
}
ll dfs(ll u, ll p){
ll msz = -1, v0 = 0;
for(ll c: G[u]){
if(c != p){
if(sz[c] > msz){
msz = sz[c];
v0 = c;
}
}
}
if(msz == -1){
update(a[u], {1ll , 1ll});
return 0;
}
ll res = 0;
for(ll c: G[u]){
if(c != p && c != v0){
res += dfs(c, u);
delete_(c, u);
}
}
res += dfs(v0, u);
ll res1 = 0, res2 = 0;
for(ll c: G[u]){
if(c != p && c != v0){
res1 += dfslow(c, u);
res2 += dfshigh(c, u);
}
}
for(ll c: G[u]){
if(c != p && c != v0){
add_(c, u);
}
}
// cout << u << ' ' << res1 << ' ' << res2;el;
return res + min(res1, res2);
}
ll timer = 0;
ll readInput(){
ll v; cin >> v;
ll myval = timer;
timer++;
if(v){
a[myval] = v;
}else{
ll c1 = readInput(), c2 = readInput();
G[c1].push_back(myval);
G[myval].push_back(c1);
G[c2].push_back(myval);
G[myval].push_back(c2);
}
return myval;
}
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
if(fopen(__file_name ".inp", "r")){
freopen(__file_name ".inp","r",stdin);
freopen(__file_name ".out","w",stdout);
}
// code here
cin >> n;
timer = 1;
ll root = readInput();
n = timer - 1;
dfs_size(root, 0);
cout << dfs(root, 0);
return 0;
}
/*
Code by: Nguyen Viet Trung Nhan
Cau Giay Secondary School
*/
