731B - Coupons and Discounts - CodeForces Solution

#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <utility>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>

using namespace std;

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
 
    int n;
    cin >> n;
    int a[n+1];
    for (int j = 0; j < n; j++)
    {
            cin >> a[j];
    }
    a[n] = 0;

    bool ans = true;
    for (int j = 0; j < n; j++)
    {
            if (a[j] < 0)
            {
                ans = false;
                break;
            }

            if (a[j] % 2 == 1)
            {
                a[j+1]--;
            }
    }
    if (a[n] < 0) ans = false;

    ans ? cout << "YES\n" : cout << "NO\n";
 
    return 0;
}