n=int(input())
f=[[0]]
for i in range(n):
    a=[0]+list(map(int,input().split()))
    f.append(a)
for i in range(n-1,0,-1):
    for j in range(1,i+1):
        f[i][j]+=max(f[i+1][j],f[i+1][j+1])

print(f[1][1])