#include "bits/stdc++.h" #include<random> using namespace std; typedef unsigned long long _ulong; typedef long long int lint; typedef pair<lint, lint> plint; typedef pair<double long, double long> pld; #define ALL(x) (x).begin(), (x).end() #define SZ(x) ((lint)(x).size()) #define FOR(i, begin, end) for(lint i=(begin),i##_end_=(end);i<i##_end_;i++) #define IFOR(i, begin, end) for(lint i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--) #define REP(i, n) FOR(i,0,n) #define IREP(i, n) IFOR(i,0,n) #define endk '\n' template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; } template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; } const lint mod = 1e9 + 7, INF = 1e18; lint dx[8] = { 0, -1, 1, 0, 1, -1, 1, -1 }, dy[8] = { 1, 0, 0, -1, -1, -1, 1, 1 }; typedef pair<double, lint> Pa; typedef pair<plint, lint> tlint; struct edge { lint cost; lint u, v; }; lint N, M, A; lint dp[1001][2]; lint sum[1000]; int main() { cin >> N >> M; REP(i, N) { REP(j, M) { cin >> A; sum[i] += A; } } REP(i, N) { REP(j, 2) { chmax(dp[i + 1][j], dp[i][j]); if (j == 0) chmax(dp[i + 1][j + 1], dp[i][j] + sum[i]); else chmax(dp[i + 1][j - 1], dp[i][j] - sum[i]); } } cout << max(dp[N][0], dp[N][1]) << endk; }