#include <fstream>

using namespace std;
ifstream cin("koba.in");
ofstream cout("koba.out");
int main()
{
    int n,sum=0;
    int a,b,c,d;
    int a1,b1,c1;
    cin>>n>>a>>b>>c;
    a%=10;
    b%=10;
    c%=10;
    a1=a;
    b1=b;
    c1=c;
    for(int i=1; i<=n-3; i++)
    {
        d=c+b*a;
        d%=10;
        sum+=d;
        a=b;
        b=c;
        c=d;
    }
    switch(n)
    {
    case 1:
        cout<<a1;
        break;
    case 2:
        cout<<a1+b1;
        break;
    case 3:
        cout<<a1+b1+c1;
        break;
    }
    if(n>=4)
        cout<<a1+b1+c1+sum;
    return 0;
}