#include<iostream>
using namespace std;
long long  arr[25][25];
int main(){
	int x,y,n,m;
	cin>>n>>m>>x>>y;
	for(int i=0;i<=n;i++)arr[i][0]=1;
	for(int i=0;i<=m;i++)arr[0][i]=1;
	arr[x][y]=-1;
	if(x-1>=0&&y-2>=0)arr[x-1][y-2]=-1;
	if(x-2>=0&&y-1>=0)arr[x-2][y-1]=-1;
	if(x-2>=0&&y+1<=m)arr[x-2][y+1]=-1;
	if(x-1>=0&&y+2<=m)arr[x-1][y+2]=-1;
	if(x+1<=n&&y+2<=m)arr[x+1][y+2]=-1;
	if(x+2<=n&&y+1<=m)arr[x+2][y+1]=-1;
	if(x+2<=n&&y-1>=0)arr[x+2][y-1]=-1;
	if(x+1<=n&&y-2>=0)arr[x+1][y-2]=-1;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			if(arr[i][j]!=-1){
				if(arr[i-1][j]!=-1)arr[i][j]+=arr[i-1][j];
				if(arr[i][j-1]!=-1)arr[i][j]+=arr[i][j-1];
			}
		}
	}
	cout<<arr[n][m];
}