// Src : Vux2Code
#include <bits/stdc++.h>
using namespace std;
template <typename T> void vout(T s){ cout << s << endl; exit(0);}
typedef long long ll;
typedef long double ld;
typedef pair <ll, ll> pll;
// ll t = 1;
const int mxn = 4e5 + 5;
int tin[mxn], tout[mxn], l[mxn], r[mxn], pos[mxn], fwk[mxn];
long long sz[mxn], dp[mxn];
int cnt = 0, n, t = 0;
void upd(int p, int val) {
for (int i = p; i <= n; i += (i & -i)) {
fwk[i] += val;
}
}
int qry(int p) {
int sum = 0;
for (int i = p; i > 0; i -= (i & -i)) {
sum += fwk[i];
}
return sum;
}
int input() {
int cur;
cin >> cur;
if (cur == 0) {
cur = ++cnt;
l[cur] = input();
r[cur] = input();
tin[cur] = tin[l[cur]];
tout[cur] = tout[r[cur]];
sz[cur] = sz[l[cur]] + sz[r[cur]];
} else {
tin[cur] = tout[cur] = ++t;
pos[t] = cur;
sz[cur]++;
}
return cur;
}
void solve(int cur, bool keep) {
if (cur <= n) {
if (keep) {
upd(pos[tin[cur]], 1);
}
return;
}
if (sz[l[cur]] < sz[r[cur]]) {
swap(l[cur], r[cur]);
}
solve(r[cur], false);
solve(l[cur], true);
long long invcnt = 0;
for (int i = tin[r[cur]]; i <= tout[r[cur]]; i++) {
invcnt += qry(pos[i]);
}
dp[cur] = dp[l[cur]] + dp[r[cur]] + min(invcnt, (sz[l[cur]] * sz[r[cur]]) - invcnt);
if (keep) {
for (int i = tin[r[cur]]; i <= tout[r[cur]]; i++) {
upd(pos[i], 1);
}
} else {
for (int i = tin[l[cur]]; i <= tout[l[cur]]; i++) {
upd(pos[i], -1);
}
}
}
void solve () {
cin >> n;
cnt = n;
input();
solve(n + 1, true);
cout << dp[n + 1];
}
int main () {
ios::sync_with_stdio (0);
cin. tie (0);
cout. tie (0);
// #define TASK "task"
// freopen (TASK".inp", "r", stdin);
// freopen (TASK".out", "w", stdout);
// cin >> t;
// while (t --) solve ();
solve ();
}
