'''

@author: olivier.massot, 2019
'''
import sys

# houses = [int(input()) for _ in range(int(input()))]
houses = [1, 15, 10, 13, 16]

print(houses, file=sys.stderr)
        
to_rob = []

def max_independent_weight(weights):
    
    def with_and_without(i):
        if i < 0 or i >= len(weights):
            return 0, 0
        right = with_and_without(i + 1)
        return weights[i] + right[1], max(right)
               
    return max(with_and_without(0))

print(max_independent_weight(houses))