n = int(input())
if n == 1:
    print(int(input().strip()))
else:
    tower = []
    for i in range(n):
        tower.append(list(map(int,input().split())))
    for i in range(n-2,-1,-1):
        for j in range(i+1):
            tower[i][j] += max(tower[i+1][j],tower[i+1][j+1])
    print(tower[0][0])