#include <iostream>
#include <fstream>
#include <climits>



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



int main()
{
    int n;
    int a,b,c,s=0,d;
    fin>>n>>a>>b>>c;
    a %= 10;
    b %= 10;
    c %= 10;
    if (n == 1)
    {
        fout<<a;
        return 0;
    }
    if (n == 2)
    {
        fout<<a+b;
        return 0;
    }
    if (n == 3)
    {
        fout<<a+b+c;
        return 0;
    }
    s = a + b + c;
    for (int i=4; i<=n; i++)
    {
        d = (c + b*a)%10;
        s += d;
        a = b;
        b = c;
        c = d;
    }
    fout<<s;
    return 0;
}