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



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



int main()
{
    int n;
    int t1,t2,t3;
    fin>>n>>t1>>t2>>t3;
    int s=t1%10+t2%10*t3%10;
    int u1=t1%10;
    int u2=t2%10;
    int u3=t3%10;
    if(n==1)
    {
        fout<<u1;
        return 0;
    }
     if(n==2)
    {
        fout<<u1+u2;
        return 0;
    }
     if(n==3)
    {
        fout<<u1+u2*u3;
        return 0;
    }
    int d;
    for(int i=4;i<=n;i++)
    {
        d=(u1+u2*u3)%10;
        s+=d;
        u3 = u2;
        u2 = u1;
        u1 = d;
    }
    fout<<s;


    return 0;
}