#include <bits/stdc++.h>
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define ii pair <int, int>
#define fi first
#define se second
#define eb emplace_back
#define sz(a) (int)(a).size()
#define all(a) (a).begin(), (a).end()
using namespace std;
const int mxN = 5e5+5;
const int mxL = 2e5+5;
int n, val[mxN], sub[mxN], tin[mxN], tout[mxN], tour[mxN], Time, cur, ans;
vector <int> valN[mxN], ch[mxN];
int newNode() {
return ++cur;
}
struct fenwickTree {
int f[mxL];
void upd(int id, int val) {
for(; id<mxL; id+=id&-id) f[id]+=val;
}
int get(int id) {
int res = 0;
for(; id>0; id-=id&-id) res+=f[id];
return res;
}
} fwt;
struct reverseFenwickTree {
int f[mxL];
void upd(int id, int val) {
for(; id>0; id-=id&-id) f[id]+=val;
}
int get(int id) {
int res = 0;
for(; id<mxL; id+=id&-id) res+=f[id];
return res;
}
} rfwt;
void input(int node) {
int x; cin >> x;
if(x == 0) {
int lfN = newNode();
input(lfN);
int rtN = newNode();
input(rtN);
ch[node].eb(lfN);
ch[node].eb(rtN);
}
else {
val[node] = x;
}
}
void pre_dfs(int u) {
tin[u] = ++Time;
tour[Time] = u;
sub[u] = 1;
for(int v:ch[u]) {
pre_dfs(v);
sub[u] += sub[v];
}
tout[u] = Time;
}
void dfs(int u) {
int bigCh = -1;
for(int v:ch[u]) if(bigCh == -1 || sub[v]>sub[bigCh]) bigCh=v;
for(int v:ch[u]) if(v != bigCh) {
dfs(v);
FOR(i,tin[v],tout[v]){
if(val[tour[i]]) {
fwt.upd(val[tour[i]], -1);
rfwt.upd(val[tour[i]], -1);
}
}
}
if(bigCh != -1) dfs(bigCh);
/// main solve
int res=0, rres=0;
for(int v:ch[u]) if(v != bigCh) {
FOR(i,tin[v],tout[v]){
if(val[tour[i]]) {
res+=fwt.get(val[tour[i]]-1);
rres+=rfwt.get(val[tour[i]]+1);
}
}
FOR(i,tin[v],tout[v]){
if(val[tour[i]]) {
fwt.upd(val[tour[i]], 1);
rfwt.upd(val[tour[i]], 1);
}
}
}
ans += min(res, rres);
if(val[u]) {
fwt.upd(val[u], 1);
rfwt.upd(val[u], 1);
}
}
int main() {
if(fopen("test.inp", "r")) {
freopen("test.inp", "r", stdin);
freopen("test.out", "w", stdout);
}
cin.tie(0)->sync_with_stdio(0);
cin >> n;
cur = 1; input(1);
pre_dfs(1);
dfs(1);
cout << ans;
}
