#include <bits/stdc++.h>

[[nodiscard]] static inline constexpr const char* solve(const uint_fast32_t N, const std::vector<uint_least32_t>& A) noexcept
{
	for (uint_fast32_t i = 1; i < N; ++i)
		if (A[i] == A[i - 1]) return "Yes";

	for (uint_fast32_t i = 2; i < N; ++i)
		if (A[i] == A[i - 2]) return "Yes";

	return "No";
}

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

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

	std::cout << solve(N, A) << '\n';
	return 0;
}