#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef long double ld;
typedef pair<int,int> P;
constexpr ll INF = (1LL << 60);
int main(){ 
  int n, m;
  cin >> n >> m;
  vector<ll> a(n, 0);
  rep(i,n) {
    rep(j,m) {
      ll b;
      cin >> b;
      a[i] += b;
    }
  }
  
  vector<ll> dp(2, 0);
  ll res = 0;
  for (int i = 0; i < n; i++) {
    vector<ll> ndp(2, 0);
    ndp[0] = max(ndp[0], dp[1] + a[i]);
    ndp[1] = max(ndp[1], dp[0] - a[i]);
    res = max(res, max(ndp[0], ndp[1]));
    dp = move(ndp);
  }

  cout << res << endl;
  return 0; 
}