#include<iostream>
#include<cstdio>
using namespace std;

int main(){
    long a,b,c,d;
    cin>>a>>b>>c>>d;
    long arr[a+1][b+1];
    for(int i = 0; i <= a; i++){
        for(int j = 0; j <= b; j++){
            if(i == c - 2 && (j == d - 1 || j == d + 1)){
                arr[i][j] =  0;
            }else if(i == c + 2 && (j == d - 1 || j == d + 1)){
                arr[i][j] =  0;
            }else if(i == c + 1 && (j == d - 2 || j == d + 2)){
                arr[i][j] =  0;
            }else if(i == c - 1 && (j == d - 2 || j == d + 2)){
                arr[i][j] =  0;
            }else if(i == c && j == d){
                arr[i][j] =  0;
            }else{
                if(i == 0 || j == 0){
                    arr[i][j] =  1;
                }else{
                    arr[i][j] = arr[i-1][j]+arr[i][j-1];
                }
            }
        }
    }
    cout<<arr[a][b]<<endl;
    return 0;
}