#include<stdio.h>
int main()
{
	int horx[9]={0,1,1,-1,-1,2,2,-2,-2};
	int hory[9]={0,2,-2,2,-2,1,-1,1,-1};
	int horse[20][20]={0};
	int memory[20][20]={0};
	int i,j,n,m,hx,hy,dx,dy;
	scanf("%d %d %d %d",&n,&m,&hx,&hy);
	for(i=0;i<9;i++)
	{
	   dx=hx+horx[i];
	   dy=hy+hory[i];
	   if(dx<0&&dx>n&&dy<0&&dy>m)continue;
	   else
	   horse[dx][dy]=1;	
	}
	for(i=1;i<=m;i++)
	{
		if(horse[0][i]==0)
		memory[0][i]=1;
		else break;
	   }  
	for(i=1;i<=n;i++)
	{
		if(horse[i][0]==0)
		memory[i][0]=1;
		else break; 
		 } 
    for(i=1;i<=n;i++)
	   {
	   for(j=1;j<=m;j++)
	   
	   	if(horse[i][j]==1)memory[i][j]=0;
		   else memory[i][j]=memory[i-1][j]+memory[i][j-1];
		   					 }
	printf("\n%d",memory[n][m]);
	return 0;									      
}