#include <stdio.h>
#include <stdlib.h>

#define INIT_VALUE 0

int a		= INIT_VALUE,
    b		= INIT_VALUE,
    k		= INIT_VALUE,
    c		= INIT_VALUE,
    **array	= NULL,
    c_counter   = INIT_VALUE;



void parse_input()
{
	scanf("%d %d %d %d", &a, &b, &k, &c);
}

int two_pow(int n)
{
	return 1 << n;
}


void init_array()
{
	int numberOfCombinations = two_pow(k), i;
	array = (int**)calloc(numberOfCombinations, sizeof(int*));

	for (i = 0; i < numberOfCombinations; i++)
	{
		array[i] = (int*)calloc(k, sizeof(int));
	}
}

void generate_array()
{
	int numberOfCombinations = two_pow(k);
	int flipper = 1, counter = 0;
	int j, i;

	for (j = k - 1; j >= 0; j--)
	{
		for (i = 0; i < numberOfCombinations; i++)
		{
			if (counter < flipper)
			{
				array[i][j] = a;
				if (c == a)
					c_counter++;
				counter++;
			}
			else 
			{
				array[i][j] = b;
				if (c == b)
					c_counter++;
				counter = (counter + 1) % (flipper * 2);
			}
		}
		flipper *= 2;
	}
}

void print_array()
{
	int numberOfCombinations = two_pow(k), i, j;
	
	for (i = 0; i < numberOfCombinations; i++)
	{
		for (j = 0; j < k; j++)
			printf("%d ", array[i][j]);
		putchar('\n');
	}
}

int main(int argc, char** argv)
{
	parse_input();
	init_array();
	generate_array();
	//print_array();

	printf("%d", c_counter);

	return EXIT_SUCCESS;
}