考虑dp。

$$S_{i,j}=S_{i-1,j}+a_{i,j}(或\sum\limits_{k=1}^ia_{k,j}) \\ \ \ \ \ \ \ \ \ \ f_{i,k}=S_{i,j}-S_{i-k,j}+\max\{0,f_{i,k}\} \\ ans=\max\limits_{1 \leq i,j \leq n,1 \leq k \leq i}f_{i,k}$$$$\int\limits_{\int\limits_{\int\limits_{\int\limits}}}$$