import java.util.*;

public class Main {
    
    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        int p = sc.nextInt()%10;
        int q = sc.nextInt()%10;
        int r = sc.nextInt()%10;
        long K = sc.nextLong()-1;
        int now = 0;
        int loop = 0;
        ArrayList<Integer> arr = new ArrayList<>();
        arr.add(p);
        arr.add(q);
        arr.add(r);
        for(;;) {
            now = (p+q+r)%10;
            arr.add(now);
            p = q;
            q = r;
            r = now;
            if( check(arr,p,q,r) != -1 ) {
                loop = check(arr,p,q,r);
                break;
            }
        }
        
        int s = arr.size();
        if( K < loop ) {
            System.out.println(arr.get((int)K));
        }else {
            K -= loop-1;
            K = K%(s-loop);
            System.out.println(arr.get((int)K+loop-1));
        }
        
    }
    
    static int check( ArrayList<Integer> arr, int p, int q, int r ) {
        
        int N = arr.size()-3;
        for( int i = 0; i < N; i++ ) {
            int x = arr.get(i);
            int y = arr.get(i+1);
            int z = arr.get(i+2);
            if( x == p && y == q && z == r ) {
                return i+3;
            }
        }
        
        return -1;
        
    }
    
}