#include<bits/stdc++.h>

using namespace std;
using ll = long long;
const ll INF = 1000000000000000000;

int main()
{
	int n, m; cin >> n >> m;
	vector<ll> a(n);
	for(int i = 0; i < n; i++) {
		for(int j = 0; j < m; j++) {
			ll t; cin >> t;
			a[i] += t;
		}
	}
	vector<vector<ll>> dp(n + 1, vector<ll>(2, -INF));
	dp[0][0] = 0;

	for(int i = 0; i < n; i++) {
		dp[i+1][1] = max({dp[i+1][1],dp[i][1],dp[i][0] + a[i]});
		dp[i+1][0] = max({dp[i+1][0],dp[i][0],dp[i][1] - a[i]});
	}
	cout << max(dp[n][0], dp[n][1]) << endl;
}