#include <fstream>

using namespace std;

const char InFile[]="koba.in";
const char OutFile[]="koba.out";

ifstream fin(InFile);
ofstream fout(OutFile);

int N,T1,T2,T3,sum=0;

int main()
{
	fin>>N>>T1>>T2>>T3;
	fin.close();

	T1%=10;
	T2%=10;
	T3%=10;
	sum=T1+T2+T3;
	for(register int i=4;i<=N;++i)
	{
		int T4=T3+T2*T1;
		T4%=10;
		sum+=T4;
		T1=T2;
		T2=T3;
		T3=T4;
	}

	fout<<sum;
	fout.close();
	return 0;
}