4 6
11 0 7 5 13 9
78 4 81 6 22 4
1 40 9 34 16 10
11 22 0 33 39 6

242

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int const MAX = 2 * 1e5 + 5;
int row[MAX], a[MAX], dp[MAX], tmp[MAX];

int main()
{
    int n, m;
    while(scanf("%d %d", &n, &m) != EOF)
    {
        memset(tmp, 0, sizeof(tmp));
        memset(dp, 0, sizeof(dp));
        for(int i = 1; i <= m * n; i++)
            scanf("%d", &a[i]);
        int cnt = 1;
        for(int i = 1; i <= m * n; i += m)
        {
            for(int j = 2; j <= m; j++)
            {
                tmp[1] = a[i];
                tmp[j] = max(tmp[j - 1], a[i + j - 1] + tmp[j - 2]);
            }
            row[cnt ++] = tmp[m];
        }
        dp[1] = row[1];
        for(int i = 2; i < cnt; i++)
            dp[i] = max(dp[i - 1], dp[i - 2] + row[i]);
        printf("%d\n", dp[cnt - 1]);
    }
}