#include<bits/stdc++.h>
#define int long long
using namespace std;
const int maxn=1e4+10;
int a[maxn][maxn];
int s,q,xm,ym,sum=0;
//int x1[maxn]={0,1,-1,0,0};
//int y[maxn]={0,0,0,1,-1};
signed main()
{
	int xm1,ym1;
//	freopen("river.in","r",stdin);
//	freopen("river.out","w",stdout);
    cin>>q>>s>>xm1>>ym1;
    xm=xm1+1;
    ym=ym1+1;
    a[xm][ym]=-1;
    a[xm-1][ym-2]=a[xm+1][ym-2]=a[xm+2][ym-1]=a[xm-2][ym-1]=a[xm+2][ym+1]=a[xm-2][ym+1]=a[xm-1][ym+2]=a[xm+1][ym+2]=-1;
    a[1][1]=1;
    for(int i=1;i<=q+1;i++){
		for(int j=1;j<=s+1;j++){
			if(a[i][j]!=-1){
					if(a[i-1][j]!=-1) a[i][j]+=a[i-1][j];
						if(a[i][j-1]!=-1) a[i][j]+=a[i][j-1];	
				}
			}
	}
//	for(int i=1;i<=q+1;i++){
//		for(int j=1;j<=s+1;j++){
//			cout<<a[i][j]<<" ";
//		}
//		cout<<endl;
//	}
	cout<<a[q+1][s+1]<<endl;
	return 0;                   
}