def knapsap_mod(nums):
    mods = [1001, 2003, 1003, 1997]
    targets = [1000000000 % mod for mod in mods]
    dp = [[[0, 0, 0, 0] for i in range(2003)] for _ in range(len(nums) + 1)]
    dp[0][0][0] = 1
    dp[0][0][1] = 1
    dp[0][0][2] = 1
    dp[0][0][3] = 1


    for i in range(len(nums)):
        for k in range(4):
            for j in range(mods[k]):
                if dp[i][j][k] == 1:
                    dp[i + 1][(j + nums[i]) % mods[k]][k] = 1
                    dp[i + 1][j][k] = 1

    n = len(nums)

    valid = {tuple(targets): []}
    while n > 0:
        new_valid = dict()
        # print(nums[n - 1])
        # print(len(valid))
        for valid_tuple, result in valid.items():
            left = tuple([(target + (mod - (nums[n - 1] % mod))) % mod for target, mod in zip(valid_tuple, mods)])

            ok = max([dp[n - 1][valid_tuple[k]][k] for k in range(4)])

            if ok == 1:
                new_valid[valid_tuple] = [x for x in result]
            ok = max([dp[n - 1][left[k]][k] for k in range(4)])
            if ok == 1:
                result.append(n - 1)
                new_valid[left] = [x for x in result]

        n -= 1
        valid = new_valid

    # print(sorted(valid))
    # if (0, 0, 0, 0) in valid:
    #     print(valid[(0, 0, 0, 0)])

    return valid[(0, 0, 0, 0)]


def __main__():
    n = int(input())
    numbers = list(map(int, input().split()))
    target = 1000000000
    # print(target % 1001, target % 1003, target % 2003)

    answer = []
    result = knapsap_mod(numbers)
    # print(result, sum([numbers[i] for i in result]))
    # print(sum([numbers[i] for i in result]) % 1001, sum([numbers[i] for i in result]) % 1003, sum([numbers[i] for i in result]) % 2003)
    if sum([numbers[i] for i in result]) == target:
        answer = result


        # print(num_at_least_k)

    print(len(answer), end=" ")
    for num in answer:
        print(num + 1, end=" ")


__main__()