def f(a):
e=enumerate;print sum(i*(x+y==i)for x,r in e(a)for y,i in e(r))
f([])
f([[2]])
f([[1,5,2],[9,4,2],[5,9,6]])
f([[0,3,0,4],[0,4,1,4],[4,3,1,2],[-2,4,-2,-1]])
f([[3,-1,3,3],[3,-1,3,1]])
ZGVmIGYoYSk6CgllPWVudW1lcmF0ZTtwcmludCBzdW0oaSooeCt5PT1pKWZvciB4LHIgaW4gZShhKWZvciB5LGkgaW4gZShyKSkKCmYoW10pCmYoW1syXV0pCmYoW1sxLDUsMl0sWzksNCwyXSxbNSw5LDZdXSkKZihbWzAsMywwLDRdLFswLDQsMSw0XSxbNCwzLDEsMl0sWy0yLDQsLTIsLTFdXSkKZihbWzMsLTEsMywzXSxbMywtMSwzLDFdXSk=