#include <fstream>
using namespace std;
ifstream fin("koba.in");
ofstream fout("koba.out");
int n,t1,t2,t3,i,x;
long long s;
int main() {
    fin>>n>>t1>>t2>>t3;
    t1%=10;
    t2%=10;
    t3%=10;
    if (n==1) {
        fout<<t1;
        return 0;
    }
    if (n==2) {
        fout<<t1+t2;
        return 0;
    }
    if (n==3) {
        fout<<t1+t2+t3;
        return 0;
    }
    s=t1+t2+t3;
    for (i=4;i<=n;i++) {
        x=(t3+(t2*t1)%10)%10;
        t1=t2;
        t2=t3;
        t3=x;
        s+=t3;
    }
    fout<<s;
    return 0;
}