#include <iostream>
using namespace std;
int main() {
    int n, m; cin >> n >> m;
    long long a[n];
    for (int i = 0; i < n; i++) {
        long long s = 0;
        for (int j = 0; j < m; j++) {
            long long x; cin >> x;
            s += x;
        }
        a[i] = s;
    }
    long long dp[2][n];
    dp[1][0] = a[0];
    dp[0][0] = 0;
    for (int i = 1; i < n; i++) {
        dp[0][i] = max(dp[0][i-1], dp[1][i-1] - a[i]);
        dp[1][i] = max(dp[1][i-1], dp[0][i-1] + a[i]);
    }
    cout << max(dp[0][n-1], dp[1][n-1]) << endl;
}