#include <bits/stdc++.h>

#include <atcoder/fenwicktree.hpp>
#include <atcoder/segtree.hpp>
#include <atcoder/modint.hpp>
#include <atcoder/dsu.hpp>
#include <atcoder/lazysegtree.hpp>

using namespace atcoder;
using namespace std;
using ll = long long;
using ull = unsigned long long;
template <class T>
using max_heap = priority_queue<T>;
template <class T>
using min_heap = priority_queue<T, vector<T>, greater<>>;
ll ll_min = numeric_limits<ll>::min();
ll ll_max = numeric_limits<ll>::max();
ll ALPHABET_N = 26;
using mint = modint998244353;
#define rep(i, n) for (ll i = (ll)0; i < (ll)n; i++)
#define rep_(i, k, n) for (ll i = (ll)k; i < (ll)n; i++)
#define all(a) a.begin(), a.end()

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	ll n;
	cin>>n;
	vector<ll> A(n);
	rep(i,n)cin>>A[i];
	bool ok = false;
	rep_(i, 1, n) if(A[i] == A[i - 1]) {
		ok = true;
		break;
	}
	rep_(i, 2, n) if(A[i] == A[i - 2]) {
		ok = true;
		break;
	}
	if(ok)cout<<"Yes\n";
	else cout<<"No\n";
	return 0;
}