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
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1
1
2
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1
1
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1
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3
1
1
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1
2
1
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1
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2
2
2
1
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1
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1
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1
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1
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1
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 4
1
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 8
1
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3
 3
2
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 3
2
2
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 2
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 4
2
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 2
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 100
1
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1
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1
1
1
1
1
1
1
1
1
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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
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1
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1
1
1
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1
 7
2
2
2
2
2
2
2
 3
2
1
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 10
2
3
3
3
3
2
2
2
3
2
 3
3
1
3
 2
3
1
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1
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3
 42
1
1
1
1
1
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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
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3
3
3
3
1
2
3
3
3
3
3
3
3
1
2
2
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3
1
1
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3
3
3
3
3
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3
1
2
3
3
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1
1
1
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3
3
3
3
1
2
3
1
2
2
2
3
3
2
1
3
3
1
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1
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2
2
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2
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1
2
2
2
2
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3
3
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1
1
 3
3
2
2
 3
3
2
3
 2
3
3
 3
2
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1
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1
1
2
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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;
const int inf = 1e9;
const int mod = 1e9 + 7;
const double eps = 1e-6;
const long long linf = 1e18;
const int MAXN = 1e2 + 10;
const int MAXM = 4e5 + 10;
const double E = 2.718281828;
const double pi = acos(-1.0);
int a[MAXN], player[3];
int main() {
  int n;
  scanf("%d", &n);
  bool flag = 1;
  player[0] = 1;
  player[1] = 2;
  player[2] = 3;
  for (int i = 0; i < n; ++i) {
    scanf("%d", &a[i]);
    if (i == 0 && a[i] == 3) flag = 0;
    if (i == 0) {
      if (player[0] == a[i]) {
        swap(player[1], player[2]);
      } else
        swap(player[0], player[2]);
    } else {
      if (a[i] == player[2]) {
        flag = 0;
      } else {
        if (player[0] == a[i]) {
          swap(player[1], player[2]);
        } else
          swap(player[0], player[2]);
      }
    }
  }
  puts(flag ? "YES" : "NO");
  return 0;
}
