#include <iostream>
#include <vector>
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4.1,sse4.2,avx,avx2,popcnt,tune=native")
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
int c = 1;
ordered_set s[400005];
long long int dfs(int x) {
int w;
cin >> w;
if (w != 0) {
s[x].insert(w);
return 0;
}
long long int res = 0, d = 0, h = 1;
{
int w = ++c;
d += dfs(w);
h *= s[w].size();
int flag = 0;
if (s[w].size() > s[x].size()) {
s[x].swap(s[w]);
flag = 1;
}
for (int v : s[w]) {
if (flag == 1) res += s[x].order_of_key(v);
else res += s[x].size() - s[x].order_of_key(v);
}
for (int v : s[w]) {
s[x].insert(v);
}
s[w].clear();
}
{
int w = ++c;
d += dfs(w);
h *= s[w].size();
int flag = 0;
if (s[w].size() > s[x].size()) {
s[x].swap(s[w]);
flag = 1;
}
for (int v : s[w]) {
if (flag == 1) res += s[x].order_of_key(v);
else res += s[x].size() - s[x].order_of_key(v);
}
for (int v : s[w]) {
s[x].insert(v);
}
s[w].clear();
}
return min(res, h - res) + d;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n;
cin >> n;
cout << dfs(1);
}
