long long paletta_sort(int N, int V[]) {
	for (int i = 0; i<N; i++) {
		if (i%2== 0 && V[i]%2==1)
			return -1;
		else if (i%2==1 && V[i]%2==0 )
			return -1;
	}
	int i = 0, j = 0, ris = 0;
	while (j<N) {
		if (V[j]==j) {
			j++;
		}
		if (V[i]>V[i+2]) {
			a = V[i+2];
			V[i]+2 = V[i];
			V[i] = a;
			ris++;
		}
	}
    return ris;
}