#include<iostream>
#include<fstream>
using namespace std;
int main ()
{
	int s,a,b,c,n,i,d;
	ifstream f("koba.in");
	ofstream g("koba.out");
	f>>n>>a>>b>>c;
	f.close();
	a=a%10;
	b=b%10;
	c=c%10;
	s=a+b+c;
	if(n==1) s=a;
	else if(n==2) s=a+b;
	else if(n==3) s=a+b+c;
	else 
		for(i=4;i<=n;i++) {
			d=(c+b*a)%10;
			a=b%10;
			b=c%10;
			c=d%10;
			s=s+d;
	}
	g<<s;
	g.close();
	return 0;
}