#include <stdio.h>
long a,b,c,d;
long n,s;
int main ()
{
    freopen ("koba.in","r",stdin);
    freopen ("koba.out","w",stdout);
    int i;
    scanf ("%ld%ld%ld%ld",&n,&a,&b,&c);
    a%=10;
    b%=10;
    c%=10;
    s+=a+b+c;
    for (i=4; i<=n; ++i)
    {
	d=a+b*c;
	d%=10;
	s+=d;
	a=b;
	b=c;
	c=d;
    }
    printf ("%ld",s);
    return 0;
}