#include "bits/stdc++.h"
using namespace std;

//#define int long long

#define ll long long
#define rep(i,n) for(ll i = 0; i < (n); i++)
#define P pair<ll,ll>
#define ld long double
ll INF = (1LL << 60);
int mod = 1000000007;

ll a[1001][1001];
ll dp[1010][1010];
signed main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	ll N, M; cin >> N >> M;
	rep(i, N) {
		rep(j, M) {
			cin >> a[i][j];
		}
	}
	vector<ll>sum(N);
	rep(i, N) {
		ll now = 0;
		rep(j, M) {
			now += a[i][j];
		}
		sum[i] = now;
	}
	rep(i, 1010)rep(j, 1010)dp[i][j] = -INF;
	dp[0][0] = 0;
	rep(i, N) {
		rep(j, 1009) {
			dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
			ll tmp = 1;
			if (j % 2 == 1)tmp = -1;
			dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j] + tmp * sum[i]);
		}
	}
	ll ans = 0;
	rep(i, 1010)ans = max(ans, dp[N][i]);
	cout << ans << endl;
	return 0;
}