Give me some tests Please!

I had WA #21 too. But there was no something special, just stupid mistake. I stored the input not in Matrix, but in Array. And I filled it wrong;
My wrong way:  (in pascal)
for i := 1 to n do
  for j := 1 to m do
    read(Mat[(i-1)*n + j]);
My correct way:
for i := 1 to n do
  for j := 1 to m do
    read(Mat[(i-1)*m + j]);
May be it will help you.
And here is test which helped me find my mistake:
2 3 6
1 1 1
1 1 1
Answer: 2.

Wow
Such an old problem and still you can add  new tests

I guess in this test one needs to add to the largest section (and N*M is not very small) -- I had a problem with 1e8 sentinel.

This test helped me a lot.

2 2 10
1 3
2 4

Output is: 5

You must write the minimum height. In your case this is 2