#include <bits/stdc++.h>
using namespace std;
#define ll long long
vector<int>p,d;
vector<ll>seg;
ll po=1;
void up(int pos){
    pos+=po;
    for (pos;pos>=1;pos/=2){
        seg[pos]++;
    }
}
ll q(int l){
    l+=po;
    ll ans=0;
    while(l>1){
        if (l%2==0){
            ans+=seg[l+1];
        }
        l/=2;
    }
    return ans;
}
long long paletta_sort(int N, int V[]) {
    for (int i=0;i<N;i++){
        if (i%2==0){
            p.push_back(V[i]);
            if (V[i]&1) return -1;
        }
        else{
            d.push_back(V[i]);
            if (V[i]%2==0) return -1;
        }
    }
    while(po<N) po*=2;
    seg.resize(2*po);
    ll ans=0;
    for (int i=0;i<p.size();i++){
        ans+=q(p[i]);
        up(p[i]);
    }
    for (int i=0;i<2*po;i++) seg[i]=0;
    for (int i=0;i<d.size();i++){
        ans+=q(d[i]);
        up(d[i]);
    }

    return ans;
}