#include<fstream.h>   
ifstream f("koba.in");   
ofstream g("koba.out");   
long n,i,s;   
int t1,t2,t3,x;   
int main()   
{   
f>>n>>t1>>t2>>t3;   
if(n==1)   
  s=t1%10;   
if(n==2)   
  s=t1%10+t2%10;   
if(n==3)   
  s=t1%10+t2%10+t3%10;   
if(n>3)   
    {s=t1%10+t2%10+t3%10;   
     for(i=4;i<=n;i++)   
     {x=(t3%10+t2%10*t1%10)%10;s+=x;t1=t2;t2=t3;t3=x;}   
    }   
g<<s;   
return 0;   
}