#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<cmath>
#define ll long long 
using namespace std;
int dx[8]={1,1,-1,-1,2,2,-2,-2},dy[8]={2,-2,2,-2,1,-1,1,-1};
ll z[21][21];
int main(){
	int n,m,x,y,i,j;
	scanf("%d%d%d%d",&n,&m,&x,&y);
	for(i=1;i<=n;i++)
	    for(j=1;j<=m;j++)
	        z[i][j]=1;
	z[x][y]=0;
	for(i=0;i<8;i++) z[x+dx[i]][y+dy[i]]=0;
	for(i=2;i<=n;i++)
		for(j=2;j<=m;j++)
			if(z[i][j]) z[i][j]=z[i-1][j]+z[i][j-1];
	printf("%lld",z[n][m]);
	return 0;
}