#include<iostream>
using namespace std;

int main(){
	int n,m,m1,m2;
	int mx[9]={0,-2,-1,1,2,-2,-1,1,2},my[9]={0,1,2,2,1,-1,-2,-2,-1}; 
	cin >> n>>m>>m1>>m2;
	n+=2,m+=2,m1+=2,m2+=2; 
	long long dp[25][25]={0};
	int judge[25][25];
	
	for(int i=0;i<9;i++){
		judge[m1+my[i]][m2+mx[i]]=1;
    }
    dp[2][1]=1;
	for (int i=2;i<=m;i++){
		for (int j=2;j<=n;j++){
			if(judge[i][j]==1) continue;			 
			dp[i][j]=dp[i-1][j]+dp[i][j-1];
		}
	}
	
	cout << dp[m][n];
	return 0;
}