#include <iostream>
#include <vector>

using namespace std;

void bfs(vector<vector<int>> &input, vector<vector<int>> &best, int score, int pos_n, int pos_m, int N, int M);

int main() {
    int N, M;
    cin >> N >> M;

    vector<vector<int>> input(N, vector<int>(M, 0));
    vector<vector<int>> best(N, vector<int>(M, 0));

    for (int i = 0; i < N; ++i) {
        for (int j = 0; j < M; ++j) {
            cin >> input[i][j];
        }
    }

    bfs(input, best, 0, 0, 0, N, M);

    cout << best[N-1][M-1] << '\n';

    return 0; 
}

void bfs(vector<vector<int>> &input, vector<vector<int>> &best, int score, int pos_n, int pos_m, int N, int M) {
    if (pos_n < 0 || pos_n >= N || pos_m < 0 || pos_m >= M) {
        return;
    }

    int current_score = score + input[pos_n][pos_m];

    if (0 != best[pos_n][pos_m]) {
        return;
    }

    best[pos_n][pos_m] = current_score;

    bfs(input, best, current_score, pos_n+1, pos_m, N, M);
    bfs(input, best, current_score, pos_n-1, pos_m, N, M);
    bfs(input, best, current_score, pos_n, pos_m+1, N, M);
    bfs(input, best, current_score, pos_n, pos_m-1, N, M);

    return;
}