#include <iostream>
#include <vector>
using namespace std;
int main(){
    int N, M;
    cin >> N >> M;
    vector<long long> sum(N, 0);
    vector<vector<long long>> A(N, vector<long long>(M));
    for(int i = 0; i < N; i++){
        for(int j = 0; j < M; j++) {
            cin >> A[i][j];
            sum[i] += A[i][j];
        }
    }
    vector<long long> dp(N + 1, -1e18);
    dp[0] = 0;
    for(int i = 0; i < N; i++){
        for(int j = 1; j < N + 1; j++){
            if(j % 2 == 0){
                dp[j] = max(dp[j], dp[j - 1] - sum[i]);
            }
            else{
                dp[j] = max(dp[j], dp[j - 1] + sum[i]);
            }
        }
    }
    long long ans = 0;
    for(int i = 0; i < N + 1; i++) ans = max(ans, dp[i]);
    cout << ans << endl;
}