Genie

Written by Fatima Amrat

Problem Statement:

English
French
Arabic
Arabic (Algeria)

1. Key Idea

Let S be the current sum of the drawn cards.
Define d = 21 - S, which represents the maximum card value you can still draw without exceeding 21.

• If the next card has value ≤ d, it is safe → draw (VUCI).
• If the next card has value > d, it is dangerous → stop (DOSTA).

2. Proof

We want to show that the strategy can be reduced to a single condition.
There are 10 possible card values: {2..9, 10, 11}, each appearing 4 times.

• Safe cards = .
• Dangerous cards = .

The condition dangerous ≥ safe simplifies to:

Therefore, the threshold occurs when S = 14:

• If S ≤ 13 → safe > dangerous → output VUCI.
• If S ≥ 14 → dangerous ≥ safe → output DOSTA.

3. Implementation

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


int main() {
  int n, sum = 0;
  cin >> n;
  
  vector<int> numbers(n);
  for(int i = 0; i < n; i++) {
    cin >> numbers[i];
    sum += numbers[i];
  }

  if (sum < 14) cout << "VUCI\n";
  else cout << "DOSTA\n";

  return 0;
}