#include<bits/stdc++.h>
#define int long long
using namespace std;
int a[29][29];
signed main(){
    int n,m;
    cin>>n>>m;
    int c,b;
    cin>>c>>b;
    a[0][1]=1;
    a[1][0]=0;
    for(int i=1;i<=n+1;i++){
        for(int j=1;j<=m+1;j++){
            if(abs(i-c)+abs(j-b)!=3&&abs(i-c)+abs(j-b)!=0)a[i][j]=a[i-1][j]+a[i][j-1];
        }
    }
    cout<<a[n+1][m+1];
    return 0;
}