#include<cstdio>
using namespace std;
long long n,m,x,y,dp[22][22];
bool vis[22][22];
int main(){
	scanf("%lld%lld%lld%lld",&n,&m,&x,&y);
	n++,m++,x++,y++;
	dp[1][1]=1;
	vis[x+2][y-1]=1;
	vis[x+2][y+1]=1;
	vis[x+1][y+2]=1;
	vis[x-1][y+2]=1;
	vis[x-2][y-1]=1;
	vis[x-2][y+1]=1;
	vis[x+1][y-2]=1;
	vis[x-1][y-2]=1;
	vis[x][y]=1;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
				if(!vis[i][j])dp[i][j]+=dp[i-1][j]+dp[i][j-1];
		}
	}
	printf("%lld",dp[n][m]);
	return 0;
}