Card game

#include <iostream>
#include <deque>
#include <algorithm>

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef std::string str;

using namespace std;

int main() {
    ll n;
    cin >> n;
    //deque<ll> costs;
    ll first, second, third;
    if (n<=2) {
      cout << 0 << endl;
      return 0;
    }
    cin >> first >> second >> third;
    ll open0 = second;
    ll open1 = 0;
    ll open2 = 0;
    ll lastCard = third;
    for (ll i=3; i<n; i++) {
      ll cur;
      cin >> cur;
      ll nextOpen0 = open2 + lastCard;
      ll nextOpen1 = max(open0, max(open1, open2));
      ll nextOpen2 = max(open1, open2);
      open0 = nextOpen0;
      open1 = nextOpen1;
      open2 = nextOpen2;
      lastCard = cur;
    }
    cout << max(open0, max(open1, open2)) << endl;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: UNKNOWN

Test 15

Verdict: UNKNOWN