def is_prime(n):
    if n == 1:
        return False
    elif n == 2:
        return True
    else:
        for x in range(2, n):
            if n % x == 0:
                return False
        return True


filename = 'lk_text.txt'
with open(filename, "r") as ins:
    array = []
    for line in ins:
        array.append(line)
newArray = []
for i in array:
    j = i.split(' ')
    k = [int(n) for n in j]
    newArray.append(k)


l = len(newArray)
for i in range(l-1):
    array1 = newArray[-1]
    array2 = newArray[-2]
    for j in range(len(array2)):
        if not (is_prime(array1[j])):
            array2[j] += max(array1[j], array1[j + 1])
    newArray.pop(-1)
    newArray[-1] = array2
print(newArray[0][0])