#check for non prime numbers
def islegal(num):
    if num > 1:
        for i in range(2, num):
            if (num % i) == 0:
                return True
        else:
            return False

    else:
        return True

#read from file
source = open('q4.txt', 'r')
row = source.readlines()
routes=[[]]
for i in range(0,len(row)):
    row[i]=row[i].split(" ")

#convert to int
for i in range(0,len(row)):
    for j in range(0,i+1):
         row[i][j]=int(row[i][j])
i=0
j=0
k=1
n=0
doublenode=[]
routes[n].append(row[i][j])


while(True):

   if k==len(row):
       if doublenode==[]:
           break

       routes.append(routes[n].copy())

       n += 1
       i, j = doublenode[-1]
       i += 1
       j += 1
       k = i
       doublenode.pop()


       while k != len(routes[n]):
           routes[n].pop()

       routes[n].append(row[i][j])
       k+=1

   #check for double nodes
   if i<len(row)-1 and islegal(row[i+1][j]) and islegal(row[i+1][j+1]) :
       doublenode.append([i, j])
       i+=1
       k+=1

       routes[n].append(row[i][j])

   elif i<len(row)-1 and islegal(row[i+1][j]) :

       i += 1
       k += 1
       routes[n].append(row[i][j])
   elif i<len(row)-1 and islegal(row[i+1][j+1]) :

       i += 1
       j += 1
       k += 1
       routes[n].append(row[i][j])
   elif i<len(row)-1 and not islegal(row[i+1][j]) and not islegal(row[i+1][j+1]) :
        if doublenode==[]:
            routes.pop()
            break
        i,j=doublenode[-1]

        i+=1
        j+=1
        k=i
        doublenode.pop()

        while k!=len(routes[n]):
            routes[n].pop()
        routes[n].append(row[i][j])
        k+=1
max=0
for i in range(0, len(routes)):
    #All possible routes
    #print(routes[i])
    if sum(routes[i])>max:
        max = sum(routes[i])

print(max)