#include <iostream>
#include <fstream>
#include <cstdlib>

void out(int x, int y, unsigned long int* z, int f, int k);
int main()
{
	using namespace std;
	unsigned long int a, b;
	unsigned long int* c = &b;
	int x, y, m, n;
	bool i;
	bool* j = &i;
	cin >> x >> y >> m >> n;
	out(x, y, c, m, n);
	a = b;
	cout << a;

	return 0;
}

void out(int x, int y, unsigned long int *z, int f, int k)
{
	unsigned long int* a = new unsigned long int[x+1];
	for (int i = 0; i <= x; i++)a[i] = 0;
	for (int i = 0; i <= y; i++)
	{
		switch (f)
		{
			case 0:
			{
				if (k == i)a[0] = 0;
				else a[0] = 1;
				break;
			}

			case 1:
			{
				if (k == i + 2)a[0] = 0;
				else
				{
					if (k == i - 2)a[0] = 0;
					else a[0] = 1;
				}
				break;
			}

			case 2:
			{
				if (k == i + 1)a[0] = 0;
				else
				{
					if (k == i - 1)a[0] = 0;
					else a[0] = 1;
				}
				break;
			}
			default:a[0] = 1;
		}
		//a[j] = a[j - 1] + a[j];
		for (int j = 1; j <= x; j++)
		{
			if (f == j && k == i)a[j] = 0;
			else
			{
				if (f == j + 1)
				{
					if (k == i + 2)a[j] = 0;
					else
					{
						if (k == i - 2)a[j] = 0;
						else
						{
							a[j] = a[j - 1] + a[j];
						}
					}
				}
				else
				{
					if (f == j - 1)
					{
						if (k == i + 2)a[j] = 0;
						else
						{
							if (k == i - 2)a[j] = 0;
							else
							{
								a[j] = a[j - 1] + a[j];
							}
						}
					}
					else
					{
						if (f == j + 2)
						{
							if (k == i + 1)a[j] = 0;
							else
							{
								if (k == i - 1)a[j] = 0;
								else
								{
									a[j] = a[j - 1] + a[j];
								}
							}
						}
						else
						{
							if (f == j - 2)
							{
								if (k == i + 1)a[j] = 0;
								else
								{
									if (k == i - 1)a[j] = 0;
									else
									{
										a[j] = a[j - 1] + a[j];
									}
								}
							}
							else
							{
								a[j] = a[j - 1] + a[j];
							}
						}
					}
				}
			}
		}
	}
	*z = a[x];
}

有点乱，qwq 有一个错了 求大佬帮忙看看awa