#include <bits/stdc++.h>
#include <atcoder/all>

using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
static const double pi = 3.141592653589793;
const ll INF = 1LL << 60;
const ll mod = 1000000007;
const ll imod = 998244353;
using mint = modint998244353;
vector<int> dx = {1, 0, -1, 0}, dy = {0, 1, 0, -1};
ll P(ll x, ll n) {
  ll ret = 1;
    while (n > 0) {
      if (n & 1) ret *= x;
      x *= x;
      n >>= 1;
  }
  return ret;
}

void seek(bool f){
  cout << (f ? "Yes" : "No") << endl;
}

int main(){
	int N;
	cin >> N;
	vector<int> A(N);
	rep(i, N){
		cin >> A[i];
	}
	for(int i = 0; i < N; i++){
		if(i + 1 < N and A[i] == A[i + 1]){
			cout << "Yes" << endl;
			return 0;
		}
		else if(i + 2 < N and A[i] == A[i + 2]){
			cout << "Yes" << endl;
			return 0;
		}
		else if(i - 2 >= 0 and A[i - 2] == A[i]){
			cout << "Yes" << endl;
			return 0;
		}
	}
	cout << "No" << endl;
}