#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll, ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
const ll MOD = 1000000007;
const ll INF = 1e18;
#define REP(i, n) for(int i = 0; i < n; i++)
#define ALL(v) v.begin(), v.end()

int main(){
	int n, m; cin >> n >> m;
	VI a(n,0); ll b;
	REP(i,n)REP(j,m){
		cin >> b;
		a[i]+=b;
	}
	VVI dp(n+1,VI(2,-INF));
	dp[0][0]=0;
	REP(i,n){
		dp[i+1][1]=dp[i][1];
		dp[i+1][0]=max(0ll,dp[i][0]);
		dp[i+1][1]=max(dp[i+1][1],dp[i][0]+a[i]);
		dp[i+1][0]=max(dp[i+1][0],dp[i][1]-a[i]);
	}
	ll ans=max(dp[n][0],dp[n][1]);
	cout << ans << endl;
	return 0;
}