#include <algorithm>
#include <iostream>
#include <memory.h>
#include <iterator>
#include <cassert>
#include <fstream>
#include <iomanip>
#include <cstdlib>
#include <bitset>
#include <vector>
#include <cstdio>
#include <string>
#include <queue>
#include <deque>
#include <cmath>
#include <ctime>
#include <stack>
#include <set>
#include <map>

//#include <tuple>
//#include <typeinfo>

using namespace std;

#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define all(x) x.begin() , x.end()

typedef long long ll;
typedef long double ld;
typedef pair < ll , ll > pll;
typedef pair < int , int > pii;

template < typename T >
T read(){
  T p = 1 , x = 0;
  char s = getchar();
  while(s == ' ' || s == '\n') s = getchar();
  if(s == '-') p = -1 , s = getchar();
  while(s >= '0' && s <= '9'){
    x = x * 10 + s - '0';
    s = getchar();
  }
  return x * p;
}

template < typename A , typename B >
void Umax(A &a , const B &b){
  if(a < b)
    a = b;
}

template < typename A , typename B >
void Umin(A &a , const B &b){
  if(a > b){
    a = b;
  }
}

ll bin_pow (ll a , ll n) {
  if(n == 0){
    return 1;
  }
  if(n % 2 == 1){
    ll cnt = a * bin_pow(a , n - 1);
    return cnt;
  }
  else {
    ll cnt = bin_pow(a , n / 2);
    return cnt * cnt;
  }
}

const int N = (int) 1e6 + 10;
const int MOD = (int) 1e9 + 7;
const int INF = (int) 1e9 + 10;
const ll LLINF = (ll) 1e18 + 10;

set <int> zz;
map <int, pair<int, bool>> m;

int main () {

  ios_base::sync_with_stdio(false);

  int n;
  cin >> n;

  for(int i = 0; i < n; ++i) {
    int x; cin >> x;

    //cout << x << endl;

    if(m[x].se == false) {
      m[x] = mp(i, true);
      zz.insert(x);
    } else {
      auto t = m[x];
      auto f = *zz.begin();

      //cout << t.fi << ' ' << ' ' << f << endl;

      if((i - t.fi + 1) % 2 == 0 && f == x) {
        m[x] = mp(0, false);
        zz.erase(f);
      } else {
        cout << "NO" << endl;
        return 0;
      }
    }
  }

  int cnt = 0;
  for(const auto &it : m) {
    if(it.se.se == true) cnt++;
  }

  if(cnt <= 1) {
    cout << "YES" << endl;
  } else {
    cout << "NO" << endl;
  }


  return 0;
}













//qwerty