99
1
3
2
2
3
1
1
3
3
3
3
3
3
1
1
3
3
3
3
1
1
3
2
1
1
1
1
1
1
1
3
2
2
2
1
3
3
1
1
3
2
1
3
3
1
2
3
3
3
1
2
2
2
3
3
3
3
3
3
2
2
2
2
3
3
3
1
1
3
2
1
1
2
2
2
3
3
2
1
1
2
2
1
3
2
1
1
2
3
3
3
3
2
2
2
2
2
1
3
 1
3
 2
2
1
 5
2
3
3
1
1
 5
2
2
2
2
2
 6
2
2
2
3
1
3
 5
2
3
3
3
3
 1
2
 100
2
2
1
3
1
3
3
1
1
3
1
1
3
2
1
3
1
1
3
3
2
2
3
1
1
2
3
2
2
3
1
1
2
3
2
1
2
2
3
3
1
1
3
1
2
1
3
1
1
3
2
2
2
1
1
1
3
1
3
2
1
2
2
2
3
3
2
1
1
3
3
2
1
2
1
1
3
1
2
3
2
3
3
3
2
2
1
3
1
2
3
1
2
3
3
1
2
1
3
1
 4
1
2
2
1
 3
3
3
1
 8
1
1
1
1
1
1
1
1
 5
1
1
1
1
3
 3
2
2
3
 3
2
2
2
 2
2
2
 4
2
3
3
3
 2
3
2
 100
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
 7
2
2
2
2
2
2
2
 3
2
1
1
 10
2
3
3
3
3
2
2
2
3
2
 3
3
1
3
 2
3
1
 3
1
2
3
 42
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
 2
1
3
 100
2
3
1
2
3
3
3
1
1
1
1
3
3
3
3
1
2
3
3
3
3
3
3
3
1
2
2
2
3
1
1
3
3
3
3
3
3
3
3
1
2
3
3
3
1
1
1
1
3
3
3
3
1
2
3
1
2
2
2
3
3
2
1
3
3
1
2
3
1
1
1
2
2
2
3
1
1
1
1
1
1
3
2
2
2
2
2
2
3
1
2
2
2
2
2
3
3
2
1
1
 3
3
2
2
 3
3
2
3
 2
3
3
 3
2
2
1
 5
1
1
2
2
3
 3
1
3
1
 3
1
1
3

YES
 NO
 NO
 NO
 YES
 NO
 YES
 YES
 NO
 NO
 NO
 YES
 NO
 NO
 YES
 YES
 YES
 NO
 YES
 YES
 NO
 NO
 NO
 NO
 NO
 YES
 YES
 YES
 NO
 NO
 NO
 YES
 NO
 NO
 NO

#include <bits/stdc++.h>
using namespace std;
int used[10000002];
int main() {
  ios::sync_with_stdio(false);
  int n, a[102], now;
  bool flag;
  while (cin >> n) {
    now = 3;
    flag = true;
    for (int i = 0; i < n; i++) cin >> a[i];
    for (int i = 0; i < n; i++) {
      if (a[i] == now) {
        flag = false;
        break;
      } else {
        if (a[i] == 1 && now == 2)
          now = 3;
        else if (a[i] == 1 && now == 3)
          now = 2;
        else if (a[i] == 2 && now == 1)
          now = 3;
        else if (a[i] == 2 && now == 3)
          now = 1;
        else if (a[i] == 3 && now == 1)
          now = 2;
        else if (a[i] == 3 && now == 2)
          now = 1;
      }
    }
    if (flag)
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  }
  return 0;
}
