#include<iostream>
using namespace std;
const int MAX = 22;
long long f[MAX][MAX] = {0};
int ctrl[MAX][MAX],n,m,hx,hy;
int d[9][2] = {{0,0},{1,2},{1,-2},{-1,2},{-1,-2},{2,1},{2,-1},{-2,1},{-2,-1}};
int main()
{
    cin >> n >> m >> hx >> hy;
    for(int i = 0;i < 9;i++)
    {
    	int tmpx = hx + d[i][0],tmpy = hy + d[i][1];
    	if(tmpx >= 0&&tmpx <= n&&tmpy >= 0&&tmpy <= m)
    	ctrl[tmpx][tmpy] = 1;
	}
	f[0][0] = 1 - ctrl[0][0];
	for(int i = 0;i <= n; i++)
	for(int j = 0;j <= m; j++)
	{
		if(ctrl[i][j]) continue;
		else if(i == 0||j == 0)
		f[i][j] = 1;
		else
		f[i][j] = f[i-1][j] + f[i][j - 1];
	}
	cout << f[n][m];
	return 0; 
	
}