#include<bits/stdc++.h>
using namespace std;
int n,m,x,y,a[55][55],b[55][55];
int main(){
    cin>>n>>m>>x>>y;
     a[x][y]=a[x+1][y+2]=a[x-1][y+2]=a[x+1][y-2]=a[x-1][y-2]=a[x+2][y+1]=a[x-2][y+1]=a[x+2][y-1]=a[x-2][y-1]=1;
    for(int i=0;i<=n;i++)
    {
        if(a[i][0]==1)
            break;
        b[i][0]=1;
    }
    for(int i=0;i<=m;i++)
    {
        if(a[0][i]==1)
            break;
        b[0][i]=1;
    }
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
            if(a[i][j]!=1)
            b[i][j]=b[i-1][j]+b[i][j-1];
    cout<<b[n][m];
    return 0;
}