#include<fstream>

using namespace std;

ifstream fin ("koba.in");
ofstream fout ("koba.out");
int main ()
{
    int n,i;
    fin>>n;
    long long unsigned s,b,c,d,a;
    fin>>a>>b>>c;
    s=a%10+b%10+c%10;
    for(i=3;i<n;i++)
    {
    d=c+b*a;
    d%=10;
    a=b;
    b=c;
    c=d;
    s+=c;
}//s=0;
//for(i=1;i<=n;i++)
//s+=(a[i]%10);
fout<<s;
return 0;
}