n,m,cx,cy=list(map(int,input().split()))
dp=[[0 for x in range(m+1)]for y in range(n+1)]
b=[[0 for x in range(m+1)]for y in range(n+1)]
p=[(-1,-2),(1,-2),(-2,-1),(2,-1),(-2,1),(2,1),(-1,2),(1,2),(0,0)]
for x in p:
if 0<=cx+x[0]<=n and 0<=cy+x[1]<=m:
b[cx+x[0]][cy+x[1]]=1
dp[0][0]=1
for x in range(1,m+1):
if b[0][x]:
dp[0][x]=0
else:
dp[0][x]=dp[0][x-1]
for x in range(1,n+1):
if b[x][0]:
dp[x][0]=0
else:
dp[x][0]=dp[x-1][0]
for x in range(1,n+1):
for y in range(1,m+1):
if b[x][y]==1:
dp[x][y]=0
else:
dp[x][y]=dp[x][y-1]+dp[x-1][y]
print(dp[n][m])
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