import java.util.Scanner;


public class Barrels {

    public static int A;
    public static int B;
    public static int L;
    public static int F;
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        while(sc.hasNextInt()) {
            A = sc.nextInt();
            B = sc.nextInt();
            
            L = sc.nextInt();
            F = sc.nextInt();
            
            System.out.println(count(0, 0));
        }
        
    }
    
    public static int count(int number, int curLength) {
        int n = 0;
        
        if(curLength == L) {
            int count = 0;
            while(number > 0) {
                int m = number % 10;
                if(m == F) count++;
                
                number /= 10;
            }
            
            return count;
        }
        
        n += count(number * 10 + A, curLength + 1);
        n += count(number * 10 + B, curLength + 1);
        
        return n;
    }
    
}