#include<bits/stdc++.h>
using namespace std;
 int n,m,x,y,a[25][25];
int main(){
   cin>>n>>m>>x>>y;
    for(int i=0;i<=n;i++){
   		for(int j=0;j<=m;j++){
   		a[i][j]=1;
		   } 
   }
   a[0][0]=1;
  a[x][y]=0;a[x-2][y-1]=0;a[x-2][y+1]=0;a[x-1][y-2]=0;a[x-1][y+2]=0;a[x+1][y-2]=0;a[x+1][y+2]=0;a[x+2][y+1]=0;a[x+2][y-1]=0;
  for(int i=0;i<=n;i++){
  		for(int j=0;j<=m;j++){
  			if(i==0&&j==0)continue;
  			if(a[i][j]==0)continue;
  			if(i==0) a[i][j]=a[i][j-1];
  			else if(j==0)a[i][j]=a[i-1][j];
  			else a[i][j]=a[i-1][j]+a[i][j-1];
		  }
  }
  cout<<a[n][m];
    return 0;
}