#include <bits/stdc++.h>

#define int int64_t

using namespace std;

void relax(int& a, int b) {
    a = max(a, b);
}

int32_t main() {
    ios_base::sync_with_stdio(false);
    int n, m;
    cin >> n >> m;
    vector<vector<int>> a(n, vector<int>(m));
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            cin >> a[i][j];
        }
    }
    vector<vector<int>> dp(n, vector<int>(m, -2e18));
    dp[0][0] = a[0][0];
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            if (i == 0 && j == 0) {
                continue;
            }
            if (i) {
                relax(dp[i][j], dp[i - 1][j] + a[i][j]);
            }
            if (j) {
                relax(dp[i][j], dp[i][j - 1] + a[i][j]);
            }
        }
    }
    cout << dp[n - 1][m - 1] << '\n';
}