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