#include<iostream>
using namespace std;
int vari[] = {0, -2, -1, 1, 2, 2, 1, -1, -2};
int varj[] = {0, 1, 2, 2, 1, -1, -2, -2, -1};//
int main(){
	long long dp[25][25]={1},x,y,n,m;
	cin >> n >> m >> x >> y;
	for(int i=0;i<=8;i++)dp[x+vari[i]][y+varj[i]]=-1;
	for(int i=0;i<=n;i++){
		for(int j=0;j<=m;j++){
			if(i==0||j==0)dp[i][j]=1;
			else if(dp[i][j]==-1)dp[i][j]=0;
			else dp[i][j]=dp[i-1][j]+dp[i][j-1];
		}
	}
	cout << dp[n][m];
	return 0;
}