#include <cmath>
#include <vector>
#include <iostream>
#include <algorithm>
#include <set>
#include <iomanip>
#include <numeric>
#include <queue>
#include <string>
#include <map>
#include <fstream>
#include <cassert>
#include <stack>
#include <climits>

int main() {
	int n, m; std::cin >> n >> m;
	std::vector<long long int> happiness(n, 0);
	for (auto& h : happiness) {
		for (auto i = 0; i < m; ++i) {
			long long int a; std::cin >> a;
			h += a;
		}
	}
	long long int odd{ 0 }, even{ LLONG_MIN >> 1};
	for (const auto h : happiness) {
		const auto o = std::max(odd, even - h);
		const auto e = std::max(even, odd + h);
		odd = o;
		even = e;
	}
	std::cout << std::max(odd, even) << '\n';
}