#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using P = pair<int, int>;
using PL = pair<lint, lint>;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
#define ALL(a)  (a).begin(),(a).end()
constexpr int MOD = 1000000007;
constexpr lint B1 = 1532834020;
constexpr lint M1 = 2147482409;
constexpr lint B2 = 1388622299;
constexpr lint M2 = 2147478017;
constexpr int INF = 2147483647;
void yes(bool expr) {cout << (expr ? "Yes" : "No") << "\n";}
int main()
{
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  lint N, M;
  cin >> N >> M;
  vector<lint> A(N);
  REP(i, N) {
    REP(j, M) {
      lint tmp = 0;
      cin >> tmp;
      A[i] += tmp;
    }
  }
  vector<vector<lint>> dp(N+1, vector<lint>(2, 0));
  REP(i, N) {
    dp[i+1][0] = dp[i][0];
    dp[i+1][1] = dp[i][1];
    dp[i+1][1] = max(dp[i+1][1], dp[i][0] + A[i]);
    if(i > 0) {
      dp[i+1][0] = max(dp[i+1][0], dp[i][1] - A[i]);
    }
  }
  cout << max(dp[N][0], dp[N][1]) << endl;
}