//#define NDEBUG
#include <cstddef>
#include <cstdint>
#include <vector>

using i8 = ::std::int_least8_t;
using i32 = ::std::int_least32_t;
using i64 = ::std::int_least64_t;
using u8 = ::std::uint_least8_t;
using u32 = ::std::uint_least32_t;
using u64 = ::std::uint_least64_t;
using isize = ::std::ptrdiff_t;
using usize = ::std::size_t;

template <class T = usize> class rep {
	const T f, l;

public:
	class itr {
		friend rep;
		T i;
		constexpr itr(T x) noexcept : i(x) {}

	public:
		void operator++() noexcept { ++i; }
		constexpr T operator*() const noexcept { return i; }
		constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
	};
	constexpr rep(const T first, const T last) noexcept : f(first), l(last) {}
	constexpr itr begin() const noexcept { return itr(f); }
	constexpr itr end() const noexcept { return itr(l); }
};
template <class T = usize> class revrep {
	const T f, l;

public:
	class itr {
		friend revrep;
		T i;
		constexpr itr(T x) noexcept : i(x) {}

	public:
		void operator++() noexcept { --i; }
		constexpr T operator*() const noexcept { return i; }
		constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
	};
	constexpr revrep(const T first, const T last) noexcept : f(first), l(last) {}
	constexpr itr begin() const noexcept { return itr(l - 1); }
	constexpr itr end() const noexcept { return itr(f - 1); }
};
template <class T> bool amax(T &a, const T &b) {
	return a <= b ? (a = b, 1) : 0;
}
template <class T> bool amin(T &a, const T &b) {
	return b <= a ? (a = b, 1) : 0;
}
template <class T> bool asmax(T &a, const T &b) {
	return b <= a ? 0 : (a = b, 1);
}
template <class T> bool asmin(T &a, const T &b) {
	return a <= b ? 0 : (a = b, 1);
}
template <class T> using vec_alias = ::std::vector<T>;
template <class T> auto md_vec(usize n, const T &value) {
	return ::std::vector<T>(n, value);
}
template <class... Args> auto md_vec(usize n, Args... args) {
	return ::std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
}
template <class T> const T &as_const(const T &v) noexcept { return v; }
template <class T> constexpr T difference(const T &a, const T &b) {
	return a <= b ? b - a : a - b;
}

#include <algorithm>
#include <iostream>
#include <utility>
#include<numeric>
#include<cassert>

int main() {
	usize n, k;
	::std::cin >> n >> k;
	::std::vector<usize> a(n), rem(n);
	for (auto &e : a) {
		::std::cin >> e;
	}

	for (const auto i : rep<>(0, n)) {
		if (a[i] < k + 1) {
			rem[i] = k + 1 - a[i];
		}
	}

	if ((k + 1) / 2 < *::std::max_element(rem.cbegin(), rem.cend())) {
		::std::cout << "-1" << ::std::endl;
		return 0;
	}
	if (k < ::std::accumulate(rem.cbegin(), rem.cend(), static_cast<usize>(0))) {
		::std::cout << "-1" << ::std::endl;
		return 0;
	}

	::std::vector<::std::pair<usize, usize>> rr(n);
	for (const auto i : rep<>(0, n)) {
		rr[i] = { rem[i],i };
	}
	::std::sort(rr.rbegin(), rr.rend());

	::std::vector<usize> rs;
	for (const auto i : rep<>(0, n)) {
		for (const auto j : rep<>(0, rr[i].first)) {
			rs.emplace_back(rr[i].second);
		}
	}


	while (rs.size() < k) {
		rs.emplace_back(rr.back().second);
	}
	const usize os = k % 2 ? k : k - 1;

	::std::vector<usize> joints(k);

	for (const auto i : rep<>(0, k)) {
		if (i * 2 < k) {
			joints[i * 2] = rs[i];
		}
		else {
			joints[i * 2 - os] = rs[i];
		}
	}
	joints.push_back(n);

	::std::vector<usize> ans;

	for (const auto v : rep<>(0, n)) {
		if (v != joints.front()) {
			ans.emplace_back(v);
		}
	}
	for (const auto i : rep<>(0, k)) {
		ans.emplace_back(joints[i]);
		for (const auto v : rep<>(0, n)) {
			if (v != joints[i] && v != joints[i + 1]) {
				ans.emplace_back(v);
			}
		}
	}

	const usize q = ans.size();

	//assert(q == (n - 1) * k + n);

	::std::cout << q << ::std::endl;

	for (const auto i : rep<>(0, q)) {
		::std::cout << ans[i] + 1 << " \n"[i + 1 == q];
	}

	


	return 0;
}


Measured memory_bytes: 256