
    Given a sequence of delivery route codes, determine the longest possible bidirectional delivery path where vehicles can traverse the same sequence of stops in both forward and reverse directions while maintaining operational efficiency. The route codes represent different delivery stops, and finding the longest palindromic subsequence will identify the most extensive symmetric route pattern that can be serviced in both directions.
    

    
def lps(str):
    """
    Given a sequence of delivery route codes, determine the longest possible bidirectional delivery path where vehicles can traverse the same sequence of stops in both forward and reverse directions while maintaining operational efficiency. The route codes represent different delivery stops, and finding the longest palindromic subsequence will identify the most extensive symmetric route pattern that can be serviced in both directions.
    

    """
def lps(str):
    """
    Given a sequence of delivery route codes, determine the longest possible bidirectional delivery path where vehicles can traverse the same sequence of stops in both forward and reverse directions while maintaining operational efficiency. The route codes represent different delivery stops, and finding the longest palindromic subsequence will identify the most extensive symmetric route pattern that can be serviced in both directions.
    

    """
    n = len(str)
    L = [[0 for x in range(n)] for x in range(n)]
    for i in range(n):
        L[i][i] = 1
    for cl in range(2, n + 1):
        for i in range(n - cl + 1):
            j = i + cl - 1
            if str[i] == str[j] and cl == 2:
                L[i][j] = 2
            elif str[i] == str[j]:
                L[i][j] = L[i + 1][j - 1] + 2
            else:
                L[i][j] = max(L[i][j - 1], L[i + 1][j])
    return L[0][n - 1]