#include<fstream.h>

int i1,i2,i3,i4,i,n,s;

int main()
{
	ifstream f("koba.in");
	ofstream g("koba.out");
	f>>n>>i1>>i2>>i3;
	i1%=10;
	i2%=10;
	i3%=10;
	i=4;
	s+=i1+i2+i3;
	while(i<=n)
	{
		i4=i3+(i2*i1)%10;
		i4%=10;
		s+=i4;
		i1=i2;
		i2=i3;
		i3=i4;
		i++;
	}
	g<<s;
	return 0;
}