#include<bits/stdc++.h>
using namespace std;
int main(){
int bx,by,m,n;
long long a[21][21]={0};
bool b[21][21]={0};
cin>>bx>>by>>m>>n;
b[m][n]=1;
if(m-1>0&&n-2>0)b[m-1][n-2]=1;
if(m-1>0)b[m-1][n+2]=1;
if(n-2>0)b[m+1][n-2]=1;
b[m+1][n+2]=1;
if(m-2>0&&n-1>0)b[m-2][n-1]=1;
if(m-2>0)b[m-2][n+1]=1;
if(n-1>0)b[m+2][n-1]=1;
b[m+2][n+1]=1;
a[1][0]=1;
a[0][1]=1;
for(int i=0;i<=bx;i++)if(!b[i][0])a[i][0]=1;
for(int i=0;i<=by;i++)if(!b[0][i])a[0][i]=1;
for(int i=1;i<=bx;i++){
	for(int j=1;j<=by;j++){
		if(!b[i][j])a[i][j]=a[i-1][j]+a[i][j-1];
	}
}
cout<<a[bx][by];
return 0;}