#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("matmax.in");
ofstream fout("matmax.out");
int main(){
    int n,m,i,j,linii,coloane,sum_prev=-0,sum_max=-3000;

    //Citire

    fin>>n>>m;
    int mat[n+1][m+1];
    for(i=1;i<=n;++i)
        for(j=1;j<=m;++j)
            fin>>mat[i][j];

    // Rezolvare

    linii=n;
    coloane=m;
    for(linii=1;linii<=n;++linii)
        for(coloane=1;coloane<=m;++coloane){
                sum_prev=0;
            for(i=1;i<=n;++i)
                for(j=1;j<=m;++j)
                    if(i>=linii && j>=coloane){
                        sum_prev=sum_prev+mat[i][j];
                    if(sum_prev>sum_max)
                        sum_max=sum_prev;
                    }
        }
    fout<<sum_max;
}