#include <fstream>

using namespace std;

ifstream fin("koba.in");
ofstream fout("koba.out");

int n, ant1, crt, ant2, ant3, s, i;

int main(){
    fin>>n>>ant3>>ant2>>ant1;
    s = ant3%10 + ant2%10 + ant1%10;
    for(i=4;i<=n;i++){
        crt = ((ant3%10) * (ant2%10) + ant1%10)%10;
        s += crt;
        ant3 = ant2;
        ant2 = ant1;
        ant1 = crt;
    }
    fout<<s;
    return 0;
}