#include <fstream>
#include <cstring>

using namespace std;

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

int n, ant1, crt, ant2, ant3, s, i, nr;
char S[100];

int main(){
    fin.get(S, 100);
    for(i=0;S[i]!=0;i++){
        if(S[i] != ' '){
            if(nr == 0)
                n = n*10 + S[i] - '0';
            if(nr == 1)
                ant3 = ant3*10 + S[i] - '0';
            if(nr == 2)
                ant2 = ant2*10 + S[i] - '0';
            if(nr == 3)
                ant1 = ant1*10 + S[i] - '0';

        }
        else
            nr++;
    }
    s = ant3%10 + ant2%10 + ant1%10;
    for(i=4;i<=n;i++){
        crt = ((ant3%10) * (ant2%10) + ant1%10)%10;
        s += crt;
        ant3 = ant2;
        ant2 = ant1;
        ant1 = crt;
    }
    fout<<s;
    return 0;
}