#include<bits/stdc++.h>
using namespace std;
int bx,by,x,y,a[1005][1005];
int main(){
    cin>>bx>>by>>x>>y;
    a[x-1][y-2]=a[x-2][y-1]=a[x-1][y+2]=a[x-2][y+1]=-1;
    a[x+1][y-2]=a[x+2][y-1]=a[x+1][y+2]=a[x+2][y+1]=a[x][y]=-1;
    for(int i=0;i<=bx;i++)
    	for(int j=0;j<=by;j++){
    		if(a[i][j]==-1){a[i][j]=0;continue;}
    		if(i==0&&j==0) a[i][j]=1;
    		else 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[bx][by];
    return 0;
}