def test1(n,m,Hx,Hy):
    dp =[[0 for i in range(m+1)] for j in range(n+1)]
    cond = [[0 for i in range(m+1)] for j in range(n+1)]
    dp[0][0]=1
    if Hy-2>=0:
       cond[Hx+1][Hy-2] = -1
       cond[Hx+2][Hy-1] = -1
    if Hx-2>=0:
       cond[Hx-2][Hy+1] = -1
       cond[Hx-1][Hy+2] = -1
    if Hy - 2 >= 0 and Hx - 1 >= 0:
        cond[Hx - 1][Hy - 2] = -1
    if Hy - 1 >= 0 and Hx - 2 >= 0:
        cond[Hx - 2][Hy - 1] = -1
    cond[Hx+2][Hy+1] = -1
    cond[Hx+1][Hy+2] = -1
    cond[Hx][Hy] = -1
    for i in range(1,n+1): #x轴 y=0
        if cond[i][0]!=-1:
           dp[i][0]=dp[i-1][0]
    for j in range(1,m+1): #y轴 x=0
        if cond[0][j]!=-1:
           dp[0][j]=dp[0][j-1]
    for i in range(1,n+1):
        for j in range(1,m+1):
            if cond[i][j]!=-1:
               dp[i][j]=dp[i-1][j]+dp[i][j-1]
    print(dp[n][m])

n, m, Hx, Hy = map(int, input().split())
test1(n,m,Hx,Hy) #马 终点