#include <bits/stdc++.h>

// O(N + M) 解法
[[nodiscard]] static inline constexpr std::vector<std::pair<uint_least32_t, uint_least32_t>> solve(const uint_fast32_t N, const uint_fast32_t M, const std::vector<uint_least32_t>& A) noexcept
{
	std::vector<std::pair<uint_least32_t, uint_least32_t>> ans;
	ans.reserve(M);
	uint_fast32_t i, j, length;
	for (i = 1, j = 0, length = 0; i <= N; ++i)
	{
		if (j != M && i == A[j]) ++length, ++j;
		else if (length != 0) ans.emplace_back(i - length, length), length = 0;
	}
	if (length != 0) ans.emplace_back(i - length, length);

	return ans;
}

static inline void output(const std::vector<std::pair<uint_least32_t, uint_least32_t>>& ans) noexcept
{
	std::cout << ans.size() << '\n';
	for (const auto& [S, L] : ans)
		std::cout << S << ' ' << L << '\n';
}

int main()
{
	std::cin.tie(nullptr);
	std::ios::sync_with_stdio(false);

	uint_fast32_t N, M;
	std::cin >> N >> M;
	std::vector<uint_least32_t> A(M);
	for (auto& a : A) std::cin >> a;

	output(solve(N, M, A));
	return 0;
}