func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long int n, a = 1, b = 2, flag = 0;     cin >> n;     long long int arr[n];     for (int i = 0; i < n; i++) {       cin >> arr[i];     }     for (int i = 0; i < n; i++) {       if (arr[i] == 1 && (a == 1 && b == 2)) {         b = 3;       } else if (arr[i] == 1 && (b == 1 && a == 2)) {         a = 3;       } else if (arr[i] == 1 && (a == 1 && b == 3)) {         b = 2;       } else if (arr[i] == 1 && (b == 1 && a == 3)) {         a = 2;       } else if (arr[i] == 2 && (a == 1 && b == 2)) {         a = 3;       } else if (arr[i] == 2 && (b == 1 && a == 2)) {         b = 3;       } else if (arr[i] == 2 && (a == 3 && b == 2)) {         a = 1;       } else if (arr[i] == 2 && (b == 3 && a == 2)) {         b = 1;       } else if (arr[i] == 3 && (a == 1 && b == 3)) {         a = 2;       } else if (arr[i] == 3 && (b == 1 && a == 3)) {         b = 2;       } else if (arr[i] == 3 && (a == 2 && b == 3)) {         a = 1;       } else if (arr[i] == 3 && (b == 2 && a == 3)) {         b = 1;       } else if (i == 0 && arr[i] == 3) {         flag = 1;         break;       } else {         flag = 1;         break;       }     }     if (flag == 0) {       cout <<  YES ;     } else {       cout <<  NO ;     }     return 0;   }   