// koba.cpp : Defines the entry point for the console application.
//

//#include "stdafx.h"
#include "fstream"
using namespace std;
int main()
{
	ifstream f("koba.in");
	ofstream g("koba.out");
	int n,t1,t2,t3;
	f>>n>>t1>>t2>>t3;
	t1%=10;
	t2%=10;
	t3%=10;
	int i,s=0;
	s=t1+t2+t3;
	if(n>=3)
	{
	for(i=0;i<n-3;i++)
	{
		int t4;
		t4=(t3+t2*t1)%10;
		t1=t2%10;
		t2=t3%10;
		t3=t4%10;
		s+=t4;
	}
	g<<s;
	}
	if(n==2)
		g<<t1+t2;
	if(n==1)
		g<<t1;	
	return 0;
}