#include <bits/stdc++.h>

using namespace std;

#define rint register int

#define IL inline

#define rep(i,h,t) for(int i=h;i<=t;i++)

#define dep(i,t,h) for(int i=t;i>=h;i--)

#define ll long long

#define me(x) memset(x,0,sizeof(x))

#define mep(x,y) memcpy(x,y,sizeof(y))

#define mid (t<=0?(h+t-1)/2:(h+t)/2)

namespace IO{

    char ss[<<],*A=ss,*B=ss;

    IL char gc()

    {

        return A==B&&(B=(A=ss)+fread(ss,,<<,stdin),A==B)?EOF:*A++;

    }

    template<class T> void read(T &x)

    {

        rint f=,c; while (c=gc(),c<||c>) if (c=='-') f=-; x=(c^);

        while (c=gc(),c>&&c<) x=(x<<)+(x<<)+(c^); x*=f;

    }

    char sr[<<],z[]; int Z,C1=-;

    template<class T>void wer(T x)

    {

        if (x<) sr[++C1]='-',x=-x;

        while (z[++Z]=x%+,x/=);

        while (sr[++C1]=z[Z],--Z);

    }

    IL void wer1()

    {

        sr[++C1]=' ';

    }

    IL void wer2()

    {

        sr[++C1]='\n';

    }

    template<class T>IL void maxa(T &x,T y) {if (x<y) x=y;}

    template<class T>IL void mina(T &x,T y) {if (x>y) x=y;}

    template<class T>IL T MAX(T x,T y){return x>y?x:y;}

    template<class T>IL T MIN(T x,T y){return x<y?x:y;}

};

using namespace IO;

const int N1=4.1e5;

const int N2=7e6;

int ch[N1][],node,v[N1],rt[N1],n;

ll ans,cnt1,cnt2;

int gettree()

{

    int x,u=++node;read(x);

    if(!x)ch[u][]=gettree(),ch[u][]=gettree();

    else v[u]=x;

    return u;

}

struct sgt{

    int sum[N2],ls[N2],rs[N2],cnt;

    void insert(int &x,int h,int t,int pos)

    {

        x=++cnt; sum[x]=;

        if (h==t) return;

        if (pos<=mid) insert(ls[x],h,mid,pos);

        else insert(rs[x],mid+,t,pos);

    }

    int merge(int x,int y)

    {

        if (!x||!y) return x^y;

        sum[x]+=sum[y];

        cnt1+=1ll*sum[ls[x]]*sum[rs[y]];

        cnt2+=1ll*sum[rs[x]]*sum[ls[y]];

        ls[x]=merge(ls[x],ls[y]);

        rs[x]=merge(rs[x],rs[y]);

        return x;

    }

}S;

void dfs(int x)

{

    if (v[x])

    {

        S.insert(rt[x],,n,v[x]); return;

    }

    dfs(ch[x][]);

    dfs(ch[x][]);

    cnt1=,cnt2=;

    rt[x]=S.merge(rt[ch[x][]],rt[ch[x][]]);

    ans+=MIN(cnt1,cnt2);

}

int main()

{

    freopen("1.in","r",stdin);

    freopen("1.out","w",stdout);

    read(n); gettree();

    dfs();

    cout<<ans<<endl;

    return ;

}