#include<iostream>
using namespace std;
int main(){
	int mapx,mapy;
	int mx,my;
	int map[30][30];
	cin>>mapx>>mapy>>mx>>my;
	for(int i=0;i<=mapx;i++){
		for(int j=0;j<=mapy;j++){
			if(i==0||j==0){
				map[i][j]=1;
			}
			if(i==mx&&j==my||i==mx-2&&j==my-1||i==mx-1&&j==my-2||i==mx+1&&j==my-2||i==mx+2&&j==my-1||i==mx+2&&j==my+1||i==mx+1&&j==my+2||i==mx-1&&j==my+2||i==mx-2&&j==my+1){
				map[i][j]=-1;
			}
		}
	}
	map[0][0]=1;
	for(int i=1;i<=mapx;i++){
		for(int j=1;j<=mapy;j++){
			if(map[i][j]!=-1){
				if(map[i-1][j]==-1&&map[i][j-1]==-1){
					map[i][j]=0;
				}
				else if(map[i-1][j]==-1){
					map[i][j]=map[i][j-1];
				}
				else if(map[i][j-1]==-1){
					map[i][j]=map[i-1][j];
				}
				else{
					map[i][j]=map[i-1][j]+map[i][j-1];
				}
			}
		}
	}
	cout<<map[mapx][mapy]<<endl;
	return 0;
}