#include <fstream.h>
int main ()
{
ifstream f ("koba.in");
ofstream g ("koba.out");

long n,ultima=0,i;
int t1,t2,t3,t4;

f>>n>>t1>>t2>>t3;
ultima=(t1%10)+(t2%10)+(t3%10);

for (i=4;i<=n;i++)
 {
   t4=((t3%10)+(t1%10)*(t2%10))%10;
   ultima+=t4;
   t1=t2;
   t2=t3;
   t3=t4;
 }
g<<ultima<<'\n';
g.close ();
return 0;
}