import java.util.*;
import java.io.*;

public class Main {
	static final int INF = 1<<30;
	static final long INFL = 1L<<60;
	static final int MOD = 1000000007;
	static final int MOD2 = 998244353;
	static List<List<Integer>> g;
	static long[][] matPow(long[][] mat, long p){
		int n = mat.length;
		long[][] ret = new long[n][n];
		for(int i = 0; i < n; i++) ret[i][i] = 1;
		long[][] pow = new long[n][n];
		for(int i = 0; i < n; i++) pow[i] = mat[i].clone();
		while(p > 0){
			if((p&1) == 1){
				ret = matMul(pow, ret);
			}
			pow = matMul(pow, pow);
			p >>= 1;
		}
		return ret;
	}
	static long[][] matMul(long[][] a, long[][] b){
		int h = a.length;
		int k = b.length;
		int w = b[0].length;
		long[][] ret = new long[h][w];
		for(int i = 0; i < h; i++){
			for(int j = 0; j < w; j++){
				for(int ij = 0; ij < k; ij++){
					ret[i][j] += (a[i][ij]*b[ij][j]);
					ret[i][j] %= 10;
				}
			}
		}
		return ret;
	}
	
	public static void main(String[] args) {
		FastScanner fs = new FastScanner();
		PrintWriter pw = new PrintWriter(System.out);
		// [1 1 1     [p    [p+q+r
		//  1 0 0  *   q  =  p 
		//  0 1 0]     r]    q]
		long p = fs.nextLong();
		long q = fs.nextLong();
		long r = fs.nextLong();
		long k = fs.nextLong();
		long[][] mat = {{1,1,1},{1,0,0},{0,1,0}};
		long[][] now = matPow(mat, k-3);
		long[][] source = {{r},{q},{p}};
		long[][] ans  = matMul(now,source);
		pw.println(ans[0][0]);
		pw.close();
	}
}

class FastScanner {
	private InputStream in = System.in;
	private byte[] buffer = new byte[1024];
	private int length = 0, p = 0;
	private boolean hasNextByte() {
		if (p < length) return true;
		else{
			p = 0;
			try{
				length = in.read(buffer);
			}catch(Exception e){
				e.printStackTrace();
			}
			if(length == 0) return false;
		}
		return true;
	}
	private int readByte() {
		if (hasNextByte() == true) return buffer[p++];
		return -1;
	}
	private static boolean isPrintable(int n) {
		return 33 <= n && n <= 126;
	}
	private void skip() {
		while (hasNextByte() && !isPrintable(buffer[p])) p++;
	}
	public boolean hasNext() {
		skip();
		return hasNextByte();
	}
	public String next() {
		if(!hasNext()) throw new NoSuchElementException();
		StringBuilder sb = new StringBuilder();
		int temp = readByte();
		while (isPrintable(temp)) {
			sb.appendCodePoint(temp);
			temp = readByte();
		}
		return sb.toString();
	}
	public int nextInt() {
		return Math.toIntExact(nextLong());
	}
	public int[] nextInts(int n) {
		int[] ar = new int[n];
		for (int i = 0; i < n; i++) ar[i] = nextInt();
		return ar;
	}
	public long[] nextLongs(int n) {
		long[] ar = new long[n];
		for (int i = 0; i < n; i++) ar[i] = nextLong();
		return ar;
	}
	public long nextLong() {
		if(!hasNext()) throw new NoSuchElementException();
		boolean minus = false;
		int temp = readByte();
		if (temp == '-') {
			minus = true;
			temp = readByte();
		}
		if (temp < '0' || '9' < temp) throw new NumberFormatException();
		long n = 0;
		while (isPrintable(temp)) {
			if ('0' <= temp && temp <= '9') {
				n *= 10;
				n += temp - '0';
			}
			temp = readByte();
		}
		return minus ? -n : n;
	}
	public char[] nextChars() {
		String s = next();
		return s.toCharArray();
	}
	public char[][] nextCharMat(int h, int w) {
		char[][] ar = new char[h][w];
		for(int i = 0; i < h; i++){
			String s = next();
			for(int j = 0; j < w; j++){
				ar[i][j] = s.charAt(j);
			}
		}
		return ar;
	}
}