#include<bits/stdc++.h>
using namespace std;
long long pl[21][21];
bool po[21][21];
int main(){
	int n,m,a,b;cin>>n>>m>>a>>b;
	po[a][b] = 1;
	po[a-1][b-2] = 1;
	po[a+1][b-2] = 1;
	po[a-2][b-1] = 1;
	po[a-2][b+1] = 1;
	po[a+1][b+2] = 1;
	po[a+2][b+1] = 1;
	po[a-1][b+2] = 1;
	po[a+2][b-1] = 1;
	for(int i=0;i<20;i++){
		if(po[i][0]) break;
		else pl[i][0] = 1;
	}
	for(int i=0;i<20;i++){
		if(po[0][i]) break;
		else pl[0][i] = 1;
	}
	for(int i=0;i<20;i++) 
	for(int i=1;i<20;i++){
		for(int j=1;j<20;j++){
			if(po[i][j]) continue;
			else pl[i][j] = pl[i-1][j] + pl[i][j-1];
		}
	}
	cout<<pl[n][m];
	return 0;
}