#!/usr/bin/env python3

def search_row(row):
    row = [a for a in row]
    for i in range(1, len(row)):
        prev, val = row[i-1], row[i]
        row[i] = max(prev + val, val)
    return max(row)

def search_rows(grid):
    return max(search_row(row) for row in grid)

def search_diagonals(grid):
    ln = len(grid)
    m = 0
    for d in range(-ln + 1, ln):
        r = search_row([grid[i][i+d]
                        for i in range(ln) if 0 <= i+d < ln])
        m = max(m, r)
    return m

def fib_gen(k, mem):
    if len(mem) > k and mem[k] != None:
        return mem[k]
    elif k < 56:
        s = 100003 - 200003*k + 300007*k**3
        s %= 1000000
        s -= 500000
    else:
        s = (fib_gen(k-24, mem) + fib_gen(k-55, mem) + 1000000) % 1000000
        s -= 500000
    mem += [None] * (k - len(mem) + 1)
    mem[k] = s
    return s


grid2 = [[-2, 5, 3, 2],
        [9, -6, 5, 1],
        [3, 2, 7, 3],
        [-1, 8, -4, 8]]

mem = []

side = 2000

grid = [[0]*side for i in range(side)]

for ri in range(side):
    for ci in range(side):
        grid[ri][ci] = fib_gen(side*ri + ci + 1, mem)

rows = search_rows(grid)
cols = search_rows(zip(*grid))
dia1 = search_diagonals(grid)
dia2 = search_diagonals([row[::-1] for row in grid])

print(max(rows, cols, dia1, dia2))