#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define ll long long
#define ull unsigned long long
#define nl '\n'
#define sz(x) int(x.size())
#define all(x) x.begin(),x.end()
#define rall(s)  s.rbegin(), s.rend()
#define getline(s) getline(cin>>ws,s)
#define ceill(n, m) (((n) / (m)) + ((n) % (m) ? 1 : 0))
#define pi  3.141592653589793
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define multi_ordered_set tree<int, null_type,less_equal<int>, rb_tree_tag,tree_order_statistics_node_update>


void Fast_IO(){
    ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
// freopen("filename.in", "r", stdin);
// freopen("filename.txt", "w", stdout);
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
#endif
}

int dx[8] = { 2, 1, -1, -2, -2, -1, 1, 2 };
int dy[8] = { 1, 2, 2, 1, -1, -2, -2, -1 };

int n,m;
vector<vector<ll>> v;
bool valid(int x,int y){
    return x>=0&&x<n&&y>=0&&y<m;
}

ll rec(int i=0,int j=0){
    if(i==n-1&&j==m-1)return v[i][j];
    if(!valid(i,j)) return (ll)1e-9;
    return v[i][j]+max(rec(i+1,j),rec(i,j+1));
}


void solve(){
    cin>>n>>m;
    v.resize(n,vector<ll>(m));
    for(int i=0;i<n;i++) {
        for (int j = 0; j < m; j++) {
            cin >> v[i][j];
        }
    }
    cout<<rec(0,0);


}

int main(){
    Fast_IO();
    int t =1;
//cin>>t;
    while(t--){
        solve();
    }
    return 0;
}