#include<iostream>
#include<vector>
#include<set>
#include<algorithm>
using namespace std;
using ll = long long;

int main(void){
  int n; cin >> n;
  vector<int> a(n);
  for(auto&x:a) cin >> x;
  for(int i=0; i<n-1; i++){
    vector<int> b=a;
    swap(b[i], b[i+1]);
    for(int j=0; j<n-1; j++){
      if(b[j]==b[j+1]){
        cout << "Yes" << endl; return 0;
      }
    }
  }
  cout << "No" << endl;
  return 0;
}