#include<fstream.h>
int t1,t2,t3,n,s=0,i,t;
int main()
{
ifstream f("koba.in");
ofstream g("koba.out");
f>>n>>t1>>t2>>t3;
s=s+t1%10+t2%10+t3%10;

for(i=4;i<=n;i++)


{
t=t3%10+(t2%10)*(t1%10);
s=s+t%10;
t1=t2; t2=t3;  t3=t;
}
g<<s;
f.close();
g.close();
return 0;
}