snarkhome.cpp

#include <iostream>

using namespace std;

int main(){

    int x, s, n;
    cin >> x >> s >> n;
    int *ar = new int[x];
    for (int i = 0; i < x; i++)
        ar[i] = 0;
    int bread;
    for (int i = 0; i < n; i++){
        cin >> bread;
        ar[bread - 1] = -1;
    }
    // START:
    // {
        for (int i = x - 2; i >= 0; i--){
            if (ar[i] == -1)
                continue;
            int min = -1;
            int lim = (i + s) > (x - 1) ? x - 1 : i + s;
            for (int j = i + 1; j <= lim; j++){
                if (ar[j] != -1)
                    if (ar[j] < min || min == -1)
                        min = ar[j];
            }
            if (min == -1){
                cout << "YES" << endl;
                return 0;
            }
            ar[i] = min + 1;
        }
        // for (int i = 0; i < x; i++){
            // cout << ar[i] << " ";
        // }
        // cout << endl;
    // }
    for (int i = 1; i < x - 1; i++){
        int lim = (i + s) > (x - 1) ? x - 1 : i + s;
        int min_count = 1, count = 0, min = -1;
        bool dif = false;
        // cout << "lim : " << lim << endl;
        for (int j = i; j < lim - 1; j++){
            if (ar[j] < 0){
                if (ar[j + 1] > 0 && (min == -1 || ar[j + 1] < min))
                    min = ar[j + 1];
                    // cout << j + 1 << " " <<  min << endl;
                continue;
            }
            if (ar[j + 1] > 0){
                if (ar[j] != ar[j + 1]){
                    dif = true;
                    count = min_count;
                    min_count = 0;
                }
                min = ar[j + 1];
                // cout << j + 1 << " " <<  min << endl;
            }
            min_count++;
        }
        if ((min_count < min && (count + min_count - 1) < min)){
            cout << "YES" << endl;
            // cout << min << endl;
            // cout << count << " " << min_count << endl << dif << endl;
            return 0;
        }
    }

    // int tmp;
    // do{
    //  cin >> tmp;
    //  if (tmp > 0){
    //      ar[tmp - 1] = -1;
    //      goto START;
    //  }
    // }while(tmp > 0);
    cout << "NO" << endl;

    return 0;
}