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

int N;

signed main(){
  cin>>N;
  vector<int> A(N);
  for(int i = 0; i < N; i++) cin>>A[i];
  bool flag = false;
  for(int i = 0; i < N - 1; i++){
  	if(A[i] == A[i+1]) flag = true;
  	if(i >= 1){
  		if(A[i+1] == A[i-1]) flag = true;
  	}
  	if(i < N-2){
  		if(A[i] == A[i+2]) flag = true;
  	}
  }
  flag ? cout << "Yes" << "\n" : cout << "No" << "\n";
}