n,m,a,b=(input().split())  
n=int(n)  
m=int(m)    
a=int(a)  
b=int(b)  
i=0  
j=0  
z=0  
c=[[a,b],[a-1,b-2],[a+1,b-2],[a-2,b-1],[a-2,b+1],[a-1,b+2],[a+1,b+2],[a+2,b-1],[a+2,b+1]]
br=[]  
for i in range(0,n+1):  
    line=[]    
    for j in range(0,m+1):  
      line.append(0)  
    br.append(line)    
br[0][0]=1  
for z in range(0, 9):  
    if c[z][0]<=n and c[z][1]<=m and c[z][0]>=0 and c[z][1]>=0:
       br[c[z][0]][c[z][1]] = -1  
for i in range(0,n+1):  
    for j in range(0,m+1):  
        if br[i][j]<0:  
            continue  
        if br[i-1][j]>0:  
            br[i][j]=br[i][j]+br[i-1][j]  
        if br[i][j-1]>0:  
            br[i][j]=br[i][j]+br[i][j-1]  
if br[m][n]==-1:  
    br[m][n]=0  
print(br[m][n])  

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