#pragma GCC optimize ("O2")
#pragma GCC target ("avx2")
#include<bits/stdc++.h>

using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (n); i++)
#define rep1(i, n) for(int i = 1; i <= (n); i++)
#define co(x) cout << (x) << "\n"
#define cosp(x) cout << (x) << " "
#define ce(x) cerr << (x) << "\n"
#define cesp(x) cerr << (x) << " "
#define pb push_back
#define mp make_pair
#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
#define Would
#define you
#define please

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);


	int N, M;
	cin >> N >> M;

	ll A[1000];
	rep(i, N) {
		rep(j, M) {
			ll a;
			cin >> a;
			A[i] += a;
		}
	}

	ll dp0 = 0, dp1 = -1e18;
	rep(i, N) {
		ll tmp = dp0;
		chmax(dp0, dp1 - A[i]);
		chmax(dp1, tmp + A[i]);
	}

	co(max(dp0, dp1));



	Would you please return 0;
}