#include <bits/stdc++.h>
using namespace std;

int main(){
	int N = 0;
	int value = 0;
	cin >> N;
	int A[N];
	
	for(int i = 0;i<= N -1; i++){
		cin >> A[i];
	}
	for(int i =0; i <= N - 3;i++){
		if(A[i] == A[i+2]){
			value++;
		}
	}
	if(value == 0){
		cout << "No" << endl;
	}else{
		cout << "Yes" << endl;
	}
}