#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;
		}
	}
	std::vector<long long int> memo(2, LLONG_MIN >> 1); memo[0] = 0;
	for (const auto h : happiness) {
		const auto odd = memo[0];
		const auto even = memo[1];
		memo[0] = std::max(odd, even - h);
		memo[1] = std::max(even, odd + h);
	}
	std::cout << *std::max_element(memo.begin(), memo.end()) << '\n';
}