# YEKTA CAN TURSUN
# We need a function to check whether the number is prime or not
# We can use basic implementation, check all number from 2 to N-1 and
# If there is not any number we can say that the number is prime
def isPrime(N):
    if N == 1:
        return False
    i = 2
    while i < N:
        # This statement check whether N/i results is integer or not
        # If it is true we can say that there is a number thus N is not prime
        if N % i == 0:
            return False
        i += 1
    return True 



# At that point, we need to implement input reader
# We can read the input and returns the value as a list object
# I am going to assume that we are reading the input from txt file 
# and it is spaced with " ", end with "\n" and there is "eof"
def readInput(adressOfFile):
    lines = []
    with open(adressOfFile) as file1:
        lines = [line.rstrip() for line in file1]

    result = []
    for x in lines:
        result2Int = [int(i) for i in x.split(" ")]
        result.append(result2Int)
    
    return result


# Let's wread the input file
inputMatrix = readInput("input1.txt")
print(inputMatrix)

# We can use recursivly try every possible ways to traverse the tree like structure and write all possible results
# Then select max value in the list
results = []
def traverse(cordinateY,cordinateX,sum):
    # Firstly lets check is prime
    if isPrime(inputMatrix[cordinateY][cordinateX]):
        return
    else:
        #Let's check are we end of the pyrimid
        if cordinateY+1 < len(inputMatrix):

            #Let's add this node's number
            sumAfter = sum + inputMatrix[cordinateY][cordinateX]
            
            # We can go down or diagonally
            # Go down 
            traverse(cordinateY+1,cordinateX,sumAfter)

            #Right diagonally
            traverse(cordinateY+1,cordinateX+1,sumAfter)
            
            # Left diagonally 
            #Let's assume that we cannot capable of go to left
            #I am assuing input is sqaure pyramid
            # We need to check that are we most left position or not
            if cordinateX != 0:
                pass
                #traverse(cordinateY+1,cordinateX-1,sumAfter)
        else:
            # We are at the end of the pyrimid
            # Adding the sum to result list and returning
            results.append(sum+inputMatrix[cordinateY][cordinateX])
            return
        
        # If we cannot go any down which can mean that 
        # this node's down node and both diagonal nodes are prime number,
        # let's add to the results
        results.append(sum+inputMatrix[cordinateY][cordinateX])
        return


# Traverse thorugh the tree like strucutre
traverse(0,0,0)

#Printing the results
print(max(results))

# NOTES It is not optimized way to do this
# Code can be further optimized