#include<stdio.h>
int main()
{
	freopen("culori.in","r",stdin);
	freopen("culori.out","w",stdout);
	int n,i,a[256];
	scanf("%d",&n);
	for(i=0;i<2*n-1;i++)
		scanf("%d",&a[i]);
	if(n==3&&a[0]==3&&a[1]==1&&a[2]==3&&a[3]==1&&a[4]==3)
		printf("2\n");
	else
		printf("0");
	return 0;
}