#include <bits/stdc++.h>
using namespace std;

int M, N, path[20010], dp[20010], ans = INT_MIN;

int main()
{
    freopen("perfecttour.in", "r", stdin);
    freopen("perfecttour.out", "w", stdout);
    memset(path, 128, sizeof(path));
    memset(dp, 128, sizeof(dp));
    cin >> M >> N;
    --N;
    for(int i = 1; i <= M; ++i)
    {
        for(int j = 1; j <= N; ++j)
        {
            int x;
            cin >> x;
            path[j] = max(path[j], x);
        }
    }
    dp[0] = 0;
    for(int i = 1; i <= N; ++i)
    {
        dp[i] = max(dp[i - 1], 0) + path[i];
        ans = max(ans, dp[i]);
    }
    cout << ans << endl;
    return 0;
}