n = int(input())
v=[]
for i in range (n):
    v.append(list(map(int,input().split())))
def find(i,j):
    if i+1==n:
        return v[i][j]
    else:
        return (max(find(i+1,j),find(i+1,j+1))+v[i][j])
                   
print(find(0,0))