#include <fstream>
using namespace std;
ifstream fin ("koba.in");
ofstream fout ("koba.out");
int n,a,b,s,c,i,d;
int main()
{
    fin>>n>>a>>b>>c;
    for (i=1; i<=n; i++)
    {
        d=c+b*a;
        d=d%10;
        s=s+d;
        a=b;
        b=c;
        c=d;
    }
    fout<<s;
    return 0;
}