#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N, M;
	cin >> N >> M;
	vector<ll> B(N);
	REP(i, N) REP(j, M) {
		ll A;
		scanf("%lld", &A);
		B[i] += A;
	}
	vector<ll> dp(2, -longINF), ndp;
	dp[0] = 0;
	REP(i, N) {
		ndp.assign(2, -longINF);
		ndp[1] = max(dp[1], dp[0] + B[i]);
		ndp[0] = max(dp[0], dp[1] - B[i]);
		swap(dp, ndp);
	}
	cout << dp[1] << endl;
}