def main():
    from sys import stdin
    tokens = map(int, stdin.read().split())
    last_row = next(tokens)
    numbers = list(tokens)
    print('Total rows:', last_row)

    def path_sum(i, row, acc):
        if row == last_row - 1:
            return numbers[i] + acc

        v = numbers[i]
        left_child_index = i + row + 1
        sum_left = path_sum(left_child_index, row + 1, v + acc)
        sum_right = path_sum(left_child_index + 1, row + 1, v + acc)
        return max(sum_left, sum_right)

    print('answer=%d' % path_sum(0, 0, 0))

main()

# Input:
# 15
# 75
# 95 64
# 17 47 82
# 18 35 87 10
# 20 04 82 47 65
# 19 01 23 75 03 34
# 88 02 77 73 07 63 67
# 99 65 04 28 06 16 70 92
# 41 41 26 56 83 40 80 70 33
# 41 48 72 33 47 32 37 16 94 29
# 53 71 44 65 25 43 91 52 97 51 14
# 70 11 33 28 77 73 17 78 39 68 17 57
# 91 71 52 38 17 14 91 43 58 50 27 29 48
# 63 66 04 68 89 53 67 30 73 16 69 87 40 31
# 04 62 98 27 23 09 70 98 73 93 38 53 60 04 23
#
# Output:
# Total rows: 15
# answer=1074