3176.py

n = input()

note = [[-1 for i in range(n)] for j in range(n)]

data = []
for i in range(n):
    data.append(raw_input().split(" "))
print data
def Foo(x,y):

    if y >= n-1:
        return int(data[y][x])
    
    
    if note[x][y] != -1:
        return note[x][y]
    
    note[x][y] = max(Foo(x,y+1),Foo(x + 1,y + 1))
    return note[x][y] + int(data[y][x])

print Foo(0,0)