#include<bits/stdc++.h>
using namespace std;
int main()
{
	long long bx,by,cx,cy,mp[30][30]={0},dt[30][30]={0};
	cin>>bx>>by>>cx>>cy;
	if(cx-1>=0&&cy-2>=0)
		mp[cx-1][cy-2]=1;
	if(cx-2>=0&&cy-1>=0)
		mp[cx-2][cy-1]=1;
	if(cx-1>=0&&cy+2<=by)
		mp[cx-1][cy+2]=1;
	if(cx-2>=0&&cy+1<=by)
		mp[cx-2][cy+1]=1;
	if(cx+1<=bx&&cy-2>=0)
		mp[cx+1][cy-2]=1;
	if(cx+1<=bx&&cy+2<=by)
		mp[cx+1][cy+2]=1;
	if(cx+2<=bx&&cy+1<=by)
		mp[cx+2][cy+1]=1;
	if(cx+2<=bx&&cy-1>=0)
		mp[cx+2][cy-1]=1;
	dt[0][0]=1;
	mp[cx][cy]=1;
	for(int i=0;i<=bx;i++)
		if(mp[i][0]==0)
			dt[i][0]=1;
	for(int j=0;j<=by;j++)
		if(mp[0][j]==0)
			dt[0][j]=1;
	for(int i=1;i<=bx;i++)
		for(int j=1;j<=by;j++)
			if(mp[i][j]==0)
				dt[i][j]=dt[i-1][j]+dt[i][j-1];
	cout<<dt[bx][by];
	return 0;
}

求问哪错了qwq