/* Ivan Nicolae - Bucuresti */
#include <stdio.h>
#include <string.h>

#define NMAX 10002
#define _fin "perle.in"
#define _fout "perle.out"

int i,n,A[NMAX];
/* A=4 B=5 C=6
   4 -> 1 | 2 | 3
   5 -> 25 | 14346
   6 -> 2 | 356 | 124 */

int B_unu(void)
{
 if (A[n-1]==2 && A[n]==5)
   return 1;
 return 0;
}

int B_doi(void)
{
 if ((A[n]==6 || A[n]==3) && (A[n-1]==1 || A[n-1]==2 || A[n-1]==3 || A[n-1]==4)
   && A[n-2]==3 && (A[n-3]==1 || A[n-3]==2 || A[n-3]==3 || A[n-3]==4) && A[n-4]==1)
   return 1;
 return 0;
}

int C_doi(void)
{
 if ((A[n]==6 || A[n]==2) && A[n-1]==5 && A[n-2]==3)
   return 1;
 return 0;
}

int C_trei(void)
{
 if ((A[n]==1 || A[n]==2 || A[n]==3 || A[n]==4) && A[n-1]==2 && A[n-2]==1)
   return 1;
 return 0;
}

void ReadData(void)
{
 int i,j;
 freopen("perle.in","r",stdin);
 freopen("perle.out","w",stdout);

 memset(A,0,sizeof(A));
 scanf("%d",&n);
 for (i=1;i<=n;i++)
    scanf("%d",&A[i]);

 while (n != 1)
      {
       int gasit=0;
       if (B_unu())
         { A[--n]=5; gasit=1;}
       if (B_doi())
         { n-=4; A[n]=5; gasit=1;}
       if (C_doi())
         { n-=2; A[n]=6; gasit=1;}
       if (C_trei())
         { n-=2; A[n]=6; gasit=1;}
       if (!gasit)
         break;
      }
 if (n==1)
   printf("1\n");
   else printf("0\n");

 fclose(stdin);
 fclose(stdout);
}

int main()
{
 ReadData();
 return 0;
}