#include <iostream>
using namespace std;

int main() {
    long long N, M; cin >> N >> M;
    long long sum[N];
    for (long long i = 0; i < N; i++) sum[i] = 0;
    for (long long i = 0; i < N; i++){
        for (long long j = 0; j < M; j++){
            long long A; cin >> A;
            sum[i] += A;
        }
    }
    long long dp[N][2];
    for (long long i = 0; i < N; i++) dp[i][0] = dp[i][1] = -1000000000000000000;
    for (long long i = 0; i < N; i++){
        if (i == 0){
            dp[i][0] = sum[i];
            continue;
        }
        dp[i][0] = dp[i - 1][0];
        dp[i][1] = dp[i - 1][1];
        dp[i][0] = max(dp[i][0], dp[i - 1][1] + sum[i]);
        dp[i][1] = max(dp[i][1], dp[i - 1][0] - sum[i]);
        dp[i][0] = max(dp[i][0], sum[i]);
        dp[i][1] = max(dp[i][1], 0 - sum[i]);
    }
    cout << max(dp[N - 1][0], dp[N - 1][1]) << endl;
}