#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(ri,n) for(int ri = (int)(n-1); ri >= 0; ri--)
#define rep2(i,x,n) for(int i = (int)(x); i < (int)(n); i++)
#define rrep2(ri,x,n) for(int ri = (int)(n-1); ri >= (int)(x); ri--)
#define repit(itr,x) for(auto itr = x.begin(); itr != x.end(); itr++)
#define rrepit(ritr,x) for(auto ritr = x.rbegin(); ritr != x.rend(); ritr++)
#define ALL(x) x.begin(), x.end()
using ll = long long;
using namespace std;

int main(){
  int n, m;
  cin >> n >> m;
  vector<ll> a(n, 0);
  rep(i, n)rep(j, m){
    ll in;
    cin >> in;
    a.at(i) += in;
  }
  a.push_back(LLONG_MAX);
  ll ans = 0;
  rep(i, n){
    ll add = a.at(i);
    bool mode = false;
    ll bf = -1;
    rep2(j, i+1, n){
      if(mode == false){
        if(a.at(j) < a.at(j+1)){
          bf = a.at(j);
          mode = true;
        }
      }else{
        if(a.at(j) > a.at(j+1)){
          add += a.at(j) - bf;
          mode = false;
        }
      }
    }
    ans = max(ans, add);
  }
  cout << ans << endl;
  return 0;
}