#include <cstdio>
#define MAX_NM 1000
using namespace std;

int n, m;
int a[MAX_NM][MAX_NM];

void read() {
    freopen("traseu.in", "r", stdin);
    scanf("%d %d", &n, &m);
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            scanf("%d", &a[i][j]);
        }
    }
    fclose(stdin);
}

void write() {
    freopen("traseu.out", "w", stdout);
    printf("%d", a[n - 1][m - 1]);
    fclose(stdout);
}

int max(int a, int b) {
    return a > b ? a : b;
}

void solve() {
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            if(i == 0 && j == 0) continue;
            int left = (j > 0 ? a[i][j - 1] : -1);
            int up = (i > 0 ? a[i - 1][j] : -1);
            a[i][j] += max(left, up);
        }
    }
}

int main() {
    read();
    solve();
    write();
    return 0;
}