#include <stdio.h>
int cifra(int n)
{
	return n%10;
}
int main()
{
	freopen("koba.in","r",stdin);
	freopen("koba.out","w",stdout);
	int n,m,p,q,s=0,i,j,t;
	scanf("%d%d%d%d",&n,&m,&p,&q);
	m=cifra(m);
	p=cifra(p);
	q=cifra(q);
	if (n>=3)
		s+=m+p+q;
	for (i=4; i<=n; i++)
	{
		t=cifra(cifra(q)+cifra((long long)p*m));
		s+=t;
		m=p;
		p=q;
		q=t;
	}
	printf("%d",s);
	return 0;
}