过河卒 python

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])