#include<bits/stdc++.h>
using namespace std;

bool b[21][21];
long fx[10] = {0, -2, -1, 1, 2, 2, 1, -1, -2};
long fy[10] = {0, 1, 2, 2, 1, -1, -2, -2, -1};

long long a[21][21];
long long n,m,nn,mm;
int main(){
    cin>>n>>m>>nn>>mm;
    n++;
    m++;
    nn++;
    mm++;
    b[nn][mm]=1;
    a[1][1]=1;
    for(long i=1;i<=8;i++) 
	{
		if(nn+fx[i]>=1 && nn+fx[i]<=n && mm+fy[i]>=1 && mm+fy[i]<=m)
		{  
			b[nn+fx[i]][mm+fy[i]]=1;  
		}   
	}  
    for(long q=1;q<=n;q++){  
    	for(long i=1;i<=m;i++){  
    		if(i==1 && q==1) continue;  
    		if(!b[q][i] ){  
    			a[q][i]=a[q-1][i]+a[q][i-1]; 
			}  
			//cout<<a[q][i]<<" ";  
		}  
		//cout<<"\n";  
    }  
    cout<<a[n][m];  
    return 0;  
}