#include<iostream>
using namespace std;
long long a[50][50];
long long n,m,x,y;
int main() 
{
    cin>>n>>m>>x>>y;
    for(int i=0;i<=n;i++)
    {
        for(int j=0;j<=m;j++)
        {
            a[i][j]=1;//全部默认都能走
        }
    }
    //马占据的点是不能走的 设置为0
    a[x][y]=0;
    if(x-1>=0 && y-2>=0 )
    {
        a[x-1][y-2]=-1;
    }
    if(x-2>=0 && y-1>=0 )
    {
        a[x-2][y-1]=-1;
    }
    if(x-2>=0 && y+1<=m )
    {
        a[x-2][y+1]=-1;
    }
    if(x-1>=0 && y+2<=m )
    {
        a[x-1][y+2]=-1;
    }
    if(x+1<=n && y+2<=m )
    {
        a[x+1][y+2]=-1;
    }
    if(x+2<=n && y+1<=m )
    {
        a[x+2][y+1]=-1;
    }
    if(x+2<=n && y-1>=0 )
    {
        a[x+2][y-1]=-1;
    }
    if(x+1<=n && y-2>=0 )
    {
        a[x+1][y-2]=-1;
    }
    //特殊的点：往下走，往右走；
    //普通的点：上边+下边
    for(int i=0;i<=n;i++)
    {
        for(int j=0;j<=m;j++)
        {
            if(i==0&&j==0)
            {
                continue;
            }
            if(a[i][j]==0)
            {
                continue;
            }
            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][j-1]+a[i-1][j];
            }
        }
    }
    cout<<a[m][n];
	return 0;
}