r=int(input())
mat=[[] for i in range(r)]
for i in range(r):
    mat[i].extend(list(map(int,input().split())))
for i in range(r-2,0,-1):
    for j in range(i+1):
        mat[i][j]+=max(mat[i+1][j],mat[i+1][j+1])
mat[0][0]+=max(mat[1][0],mat[1][1])
print(mat[0][0])