#include <bits/stdc++.h>
using namespace std;
const int N = 4e5+7;
int n, t;
int tree[N];
int l[N], r[N], lt[N], rt[N];
vector<int> p;
long long ans;
void add(int v, int x) {
for (; v < N; v|=v+1)
tree[v] += x;
}
int sum(int v) {
int ans = 0;
for (; v >= 0; v = (v&(v+1))-1)
ans += tree[v];
return ans;
}
int dfs() {
int x; cin>>x;
if (x) {
l[t] = r[t] = p.size();
p.push_back(x-1);
} else {
int left = dfs(), right = dfs();
l[t] = min(l[left], l[right]);
r[t] = max(r[left], r[right]);
lt[t] = left; rt[t] = right;
}
return t++;
}
void dfsSolve(int v, bool store) {
if (l[v] == r[v]) {
if (store)
add(p[l[v]], 1);
return;
}
if (r[rt[v]]-l[rt[v]] > r[lt[v]]-l[lt[v]])
swap(lt[v], rt[v]);
dfsSolve(rt[v], 0);
dfsSolve(lt[v], 1);
long long res = 0;
for (int x = l[rt[v]]; x <= r[rt[v]]; x++)
res += sum(p[x]);
ans += min(res, 1LL*(r[rt[v]]-l[rt[v]]+1)*(r[lt[v]]-l[lt[v]]+1)-res);
if (store)
for (int x = l[rt[v]]; x <= r[rt[v]]; x++)
add(p[x], 1);
else
for (int x = l[lt[v]]; x <= r[lt[v]]; x++)
add(p[x], -1);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n;
ans = t = 0;
dfsSolve(dfs(), 0);
cout << ans << endl;
return 0;
}
