#include <fstream>

using namespace std;

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

int n, t1, t2, t3;

int main() {
    fin >> n >> t1 >> t2 >> t3;
    if(n == 1) {
        fout << (t1 % 10);
    } else if(n == 2) {
        fout << (t1 % 10 + t2 % 10);
    } else {
        t1 %= 10, t2 %= 10, t3 %= 10;
        long long int s = t1 + t2 + t3;
        for(int i = 4; i <= n; i++) {
            int ti = (t3 + t2 * t1) % 10;
            s += ti;
            t1 = t2 % 10;
            t2 = t3 % 10;
            t3 = ti % 10;
        }
        fout << s;
    }
    return 0;
}