#include <iostream>
using namespace std;

int main()
{
	short h1,h2,ch1,ch2;
	cin>>ch1>>ch2>>h1>>h2;
	unsigned long long chepu[ch1+4][ch2+4];
	for(int i=0;i<=ch1;i++)
	{
	    chepu[i][0]=1;
	}
	for(int j=0;j<=ch2;j++)
	{
	    chepu[0][j]=1;
	}
	chepu[h1-2][h2-1]=0;
	chepu[h1-1][h2-2]=0;
	chepu[h1-2][h2+1]=0;
	chepu[h1-1][h2+2]=0;
	chepu[h1+1][h2-2]=0;
	chepu[h1+2][h2-1]=0;
	chepu[h1+2][h2+1]=0;
	chepu[h1+1][h2+2]=0;
	chepu[h1][h2]=0;
	for(int k=1;k<=ch1;k++)
	{
	    for(int l=1;l<=ch2;l++)
	    {
	        if(chepu[k][l]!=0)
	        {
	            chepu[k][l]=chepu[k-1][l]+chepu[k][l-1];
	        }
	    }
	}
	cout<<chepu[ch1][ch2];
    return 0;
}