def posMax_(L):
    pos = 0
    for i in range(1, len(L)):
        if L[i] > L[pos]:
            pos = i
    return pos

def buildMaxMat(T):
    l = len(T)
    c = len(T[0])
    M = matrix.init(l, c, 0)
    for j in range(c):
        M[0][j] = T[0][j]
    for m in range(1, l):
        for i in range(0,c):
            M[m][i] = T[m][i]+max_choice(M[m-1],i)
    return M

def HarryPotter(T):
    M = buildMaxMat(T)
    n = len(M)
    return (M[n-1][posMax_(M[n-1])])

def max_choice(L,indice):
    largest = L[indice]
    if (indice >=1) and (L[indice-1] > largest):
        largest = L[indice-1]
    if (indice < len(L)-1) and (L[indice+1] > largest):
        largest = L[indice+1]
    return largest