#include<stdio.h>
long n,t1,t2,t3,c,s;
int main()
{
	freopen("koba.in","r",stdin);
	freopen("koba.out","w",stdout);

	scanf("%ld",&n);
	scanf("%ld %ld %ld",&t1,&t2,&t3);
	s=(t1%10+t2%10+t3%10);
	n=n-3;
	while(n)
	{
		c=s;
		s+=(t1%10+((t2%10)*(t3%10))%10)%10;
		t1=t2%10;
		t2=t3%10;
		t3=(s-c)%10;
		n--;
	}
	printf("%ld",s);
	return 0;
}