#include <stdio.h>

#define INIT_VALUE 0
#define ARRAY_SIZE 500
#define EXIT_SUCCESS 0

int a		= INIT_VALUE,
    b		= INIT_VALUE,
    k		= INIT_VALUE,
    c		= INIT_VALUE;

char result[ARRAY_SIZE];

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

int parse_char(char x)
{
	switch (x)
	{
		case '0':
		return 0;
		case '1':
		return 1;
		case '2':
		return 2;
		case '3':
		return 3;
		case '4':
		return 4;
		case '5':
		return 5;
		case '6':
		return 6;
		case '7':
		return 7;
		case '8':
		return 8;
		case '9':
		return 9;
	}

	return -1;

}

char parse_int(int i)
{
		switch (i)
	{
		case 0:
		return '0';
		case 1:
		return '1';
		case 2:
		return '2';
		case 3:
		return '3';
		case 4:
		return '4';
		case 5:
		return '5';
		case 6:
		return '6';
		case 7:
		return '7';
		case 8:
		return '8';
		case 9:
		return '9';
	}

	return 'x';

}

void _memset(char* array, char value, int reps)
{
	int i;
	for (i = 0; i < reps; i++)
	{
		array[i] = value;
	}
}

void multiply_string(int n)
{
	int number, temp, calc, temp2 = 0, i, j, multiplicator; 
	char sum[ARRAY_SIZE];

	_memset(sum, '0', ARRAY_SIZE);
	if (n >= 10)
	{
		j = 0;
		while (n > 0)
		{
			multiplicator = n % 10;	
			if (multiplicator == 0)
			{
				n = (n / 10);
				j++;
				continue;
			}
			temp2 = 0;
			for (i = ARRAY_SIZE - 1; i >= 0; i--)
			{
				// NACITANIE CISLICE
				number = parse_char(result[i]);

				// VYPOCITAM SUCIN
				calc = number * multiplicator;
				// VYPOCITAM ZVYSOK
				temp = calc >= 10 ? (calc - (calc % 10)) / 10 : 0;
				// ZOBERIEM LEN JEDNOTKY
				calc = calc % 10;
				//NASOBKY DESIATOK
				if (j > 0)
				{	
					if ((parse_char(sum[i - j]) + calc + temp2) >= 10)
						{
							temp = ((parse_char(sum[i - j]) + calc + temp2) - ((parse_char(sum[i - j]) + calc + temp2) % 10)) / 10;
							sum[i - j] = parse_int((parse_char(sum[i - j]) + calc + temp2) % 10);
						}
					else
						sum[i - j] = parse_int(parse_char(sum[i - j]) + calc + temp2);
				}
				else
				{
					if ((calc + temp2) >= 10)
					{
						temp = ((calc + temp2) - ((calc + temp2) % 10)) / 10;
						sum[i] = parse_int((calc + temp2) % 10);
					}
					else
						sum[i] = parse_int(calc + temp2);
				}

 				temp2 = temp;
			}
			n = (n - multiplicator) / 10;
			j++;

		}
		for (i = 0; i < ARRAY_SIZE; i++)
			result[i] = sum[i];
		return;
	}
	for (i = ARRAY_SIZE - 1; i >= 0; i--)
	{	
		number = parse_char(result[i]);
		calc = number * n;
		temp = calc >= 10 ? (calc - (calc % 10)) / 10 : 0;
		calc = calc % 10;
		result[i] = parse_int(calc + temp2);
 		temp2 = temp;
	}
}

void print_string_number()
{
	int i;
	for (i = 0; i < ARRAY_SIZE; i++)
	{
		if (result[i] != '0')
		{	
			printf("%s", result + i);
			break; 
		}
		
	}
}

void two_pow(int n)
{
	int i;
	for (i = 0; i < n; i++)
		multiply_string(2);

	multiply_string(k);
}

int main(int argc, char** argv)
{
	parse_input();

	_memset(result, '0', ARRAY_SIZE);	
	result[ARRAY_SIZE - 1] = '1';

	two_pow(k - 1);

	if (c == a || c == b)	
		print_string_number();
	else puts("0");

	return EXIT_SUCCESS;
}