#include <vector>
#include <bits/stdc++.h>
using namespace std;

long long paletta_sort(int N, int V[]) {
    for (int i = 0; i < N; i++)
    {
        if(i%2!=V[i]%2) return -1;
    }
    long long ordinamenti = 0;
    for(int parita = 0; parita < 2; parita++) {
        vector<int> ft (N / 2 + 2, 0);
        int count = 0;
        for (int i = parita; i < N; i+=2)
        {
            int idx = V[i] / 2 + 1;
            int sum = 0;
            for(int j = idx; j > 0; j -= j & -j) sum += ft[j];
            ordinamenti += count - sum;
            for (int j = idx; j < ft.size(); j += j & -j) ft[j]++;
            count++;        
        }
    }
    return ordinamenti;
}