#include<iostream>
using namespace std;

int mx1[]={0,-2,-1,1,2,2,1,-1,-2};
int my1[]={0,1,2,2,1,-1,-2,-2,-1};

int bx,by,mx,my;
int f[30][30];
int m[30][30];

int main(){

	cin>>bx>>by>>mx>>my;
	m[mx][my] = 1;
	
	for(int i=1;i<=8;i++){ 
		m[mx+mx1[i]][my+my1[i]] = 1 ;
	}
	
	for(int i=0;i<=bx;i++){
		for(int j=0;j<=by;j++){
			
			
			if(m[i][j]){continue;}
			
			if(i==0&&j==0){continue;}
			
			if(i==0||j==0){
				f[i][j]=1;
			}else{
				f[i][j] = f[i-1][j]+f[i][j-1];
			}
		}
	}
	printf("%lld\n", f[bx][by]);
	return 0;
}