using namespace std;
long long a[30][30];
long long book[30][30],sum[30][30];
long long x,y,CHx,CHy;

int main()
{
   cin>>x>>y>>CHx>>CHy;
   x+=2;
   y+=2;
   CHx+=2;
   CHy+=2;
   for(int i=2;i<30;i++){
   	sum[i][0]=1;
   	sum[0][i]=1;
   }
   a[CHx][CHy]=1;
   
   a[CHx+1][CHy-2]=1;
   a[CHx-1][CHy-2]=1;
   
   a[CHx+1][CHy+2]=1;
   a[CHx-1][CHy+2]=1;
   
   a[CHx+2][CHy-1]=1;
   a[CHx-2][CHy-1]=1;
   
   a[CHx+2][CHy+1]=1;
   a[CHx-2][CHy+1]=1;
   
   sum[1][2]=1;
   for(int i=2;i<=x;i++){
   	for(int j=0;j<=y;j++){
   		if(a[i][j]==1){
   			continue;
   		}
   		sum[i][j]=sum[i][j-1]+sum[i-1][j];		
   	}
   }
   cout<<sum[x][y];
   return 0;
} ```