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#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,m,x,y,dp[25][25],vis[25][25];
int d1[8]={-2,-2,-1,-1,1,1,2,2};
int d2[8]={-1,1,-2,2,-2,2,-1,1};
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>m>>x>>y;
	for(int i=0;i<8;i++){
		if(x+d1[i]<0||x+d1[i]>n||y+d2[i]<0||y+d2[i]>m){
			continue;
		}else{
			vis[x+d1[i]][y+d2[i]]=1;
		}
	}
	vis[x][y]=1;
	if(vis[0][0]==0){
		dp[0][0]=1;
	}
	for(int i=0;i<=n;i++){
		for(int j=0;j<=m;j++){
			if(vis[i][j]==0&&dp[i][j]!=1){
				dp[i][j]=dp[i-1][j]+dp[i][j-1];
			}
		}
	}
	cout<<dp[n][m];
	return 0;
}