import java.io.*; import java.util.*; import java.util.stream.*; public class Main { static final int MOD = 10; public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); int[] ans = new int[]{sc.nextInt() % MOD, sc.nextInt() % MOD, sc.nextInt() % MOD}; long k = sc.nextLong() - 1; int[][][] matrix = new int[60][3][3]; matrix[0] = new int[][]{{0, 1, 0}, {0, 0, 1}, {1, 1, 1}}; for (int i = 1; i < 60; i++) { for (int a = 0; a < 3; a++) { for (int b = 0; b < 3; b++) { for (int c = 0; c < 3; c++) { matrix[i][a][c] += matrix[i - 1][a][b] * matrix[i - 1][b][c] % MOD; matrix[i][a][c] %= MOD; } } } } for (int i = 59; i >= 0; i--) { if (k < (1L << i)) { continue; } k -= (1L << i); int[] next = new int[3]; for (int a = 0; a < 3; a++) { for (int b = 0; b < 3; b++) { next[a] += matrix[i][a][b] * ans[b] % MOD; next[a] %= MOD; } } ans = next; } System.out.println(ans[0]); } } class Utilities { static String arrayToLineString(Object[] arr) { return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n")); } static String arrayToLineString(int[] arr) { return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new)); } } class Scanner { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st = new StringTokenizer(""); StringBuilder sb = new StringBuilder(); public Scanner() throws Exception { } public int nextInt() throws Exception { return Integer.parseInt(next()); } public long nextLong() throws Exception { return Long.parseLong(next()); } public double nextDouble() throws Exception { return Double.parseDouble(next()); } public int[] nextIntArray() throws Exception { return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); } public String next() throws Exception { while (!st.hasMoreTokens()) { st = new StringTokenizer(br.readLine()); } return st.nextToken(); } }