OJ Board

it means if you have subway line description like this:
0 0 0 1 1 0 -1 -1
then, you cannot using subway directly from (0,0) to (1, 0) .

I used dp knapsack, but why wa?

#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <cstring>
#include <iostream>
#include <vector>
#include <queue>
#include <stack>
#include <string>
#include <set>
#include <map>
#include <algorithm>

#define FOR(i, a, b) for(int i ...

@FelixP

For any particular opera, he can opt not to drive to the store to buy it, since he can just order it from Amazon.

May your algorithm didn't cover it.