#include<bits/stdc++.h>
using namespace std;
int pianyi[9][2]={{0,0},{1,2},{2,1},{2,-1},{1,-2},{-1,-2},{-2,-1},{-2,1},{-2,1}};
long long ans[21][21];
int main(){
	int n,m,hx,hy;
	cin>>n>>m>>hx>>hy;
	if(hx==0&&hy==0){
		cout<<0;
		return 0;}
	for(int i=0;i<9;i++){
		if(hx+pianyi[i][0]>=0&&hx+pianyi[i][0]<=n&&hy+pianyi[i][1]>=0&&hy+pianyi[i][1]<=m)
			ans[hx+pianyi[i][0]][hy+pianyi[i][1]]=-1;}
	ans[0][0]=1;
	for(int i=0;i<=n;i++){
		for(int j=0;j<=m;j++){
			if(ans[i][j]==-1){
				ans[i][j]=0;
				continue;} 
			if(i) ans[i][j]+=ans[i-1][j];
			if(j) ans[i][j]+=ans[i][j-1];}}
	cout<<ans[n][m];
	return 0;
}