#include <stdio.h>
int main()
{
	long long map[21][21];
	int i, j;
	int m, n, x, y;
	scanf("%d %d %d %d", &m, &n, &x, &y);

	for (i = 0; i <= m; i++) {
		for (j = 0; j <= m; j++) {
			map[i][j] = 1;
		}
	}

	int hx[8] = { -2, -2, -1, +1, +2, +2, +1, -1 };
	int hy[8] = { -1, +1, +2, +2, +1, -1, -2, -2 };
	map[x][y] = 0;
	for (i = 0; i < 8; i++) {
		if (x - hx[i] >= 0 && y - hy[i] >= 0)
			map[x - hx[i]][y - hy[i]] = 0;
	}

	for (i = 0; i <= m; i++) {
		for (j = 0; j <= m; j++) {
			if (map[i][j] == 0) continue;
			else if (i == 0 && j == 0) continue;
			else if (i == 0) map[i][j] = map[i][j - 1];
			else if (j == 0) map[i][j] = map[i - 1][j];
			else map[i][j] = map[i - 1][j] + map[i][j - 1];
		}
	}

	printf("%lld", map[m][n]);

	return 0;
}