#include <fstream>
#include <iostream>

using namespace std;
ifstream fin("koba.in");
ofstream fout("koba.out");
int n,a,b,c,d,i;
long long sol;
int main()
{
    sol=a%10+b%10+c%10;
    cin>>n>>a>>b>>c;
    for(i=4;i<=n;i++){
        d=c%10+(a%10)*(b%10);
        sol+=d%10;
        a=b;
        b=c;
        c=d;
    }
    cout<<sol;

    return 0;
}