using System;

public class Program

{

    public static int[] NhapMang() {

        int[] A;

        int N = int.Parse(Console.ReadLine());

        A = new int[N];

        for (int i=0 ; i<A.Length ; i++) {

            A[i] = int.Parse(Console.ReadLine());

        }

        return A;

    }

    public static bool GiaTriChan(int x) {

        if (x%2 == 0) {

            return true;

        }

        else {

            return false;

        }

    }

    public static void Main()

    {

        int[] A = NhapMang();

        bool check = false;

        int ans = 0;

        for (int i=0 ; i<A.Length ; i++) {

            if (GiaTriChan(A[i])) {

                check = true;

                ans = i;

                break;

            }

        }

        if (check == true) {

            Console.WriteLine(ans);

        }

        else {

            Console.WriteLine("-1");

        }

    }

}