#include <bits/stdc++.h>
using namespace std;
#define L(i, l, r) for(ll i = (l); i < (r); i++)
#define R(i, l, r) for(ll i = (l); i > (r); i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) (ll)((x).size())
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using pl = pair<ll, ll>;

int main() {
  ll n;
  cin >> n;
  vl a(n);
  L(i, 0, n) cin >> a[i];
  
  L(i, 0, n - 1){
    swap(a[i], a[i + 1]);
    L(j, 0, n - 1){
      if(a[j] == a[j + 1]){
        cout << "Yes" <<endl;
        return 0;
      } 
    } 
    swap(a[i], a[i + 1]);
  }
  cout << "No" <<endl;
  return 0;
}