Anya and Ghosts CodeForces

Anya and Ghosts

 

Anya loves to watch horror movies. In the best traditions of horror, she will be visited by m ghosts tonight. Anya has lots of candles prepared for the visits, each candle can produce light for exactly t seconds. It takes the girl one second to light one candle. More formally, Anya can spend one second to light one candle, then this candle burns for exactly t seconds and then goes out and can no longer be used.

For each of the m ghosts Anya knows the time at which it comes: the i-th visit will happen w_i seconds after midnight, all w_i's are distinct. Each visit lasts exactly one second.

What is the minimum number of candles Anya should use so that during each visit, at least r candles are burning? Anya can start to light a candle at any time that is integer number of seconds from midnight, possibly, at the time before midnight. That means, she can start to light a candle integer number of seconds before midnight or integer number of seconds after a midnight, or in other words in any integer moment of time.

Input

The first line contains three integers m, t, r (1 ≤ m, t, r ≤ 300), representing the number of ghosts to visit Anya, the duration of a candle's burning and the minimum number of candles that should burn during each visit.

The next line contains m space-separated numbers w_i (1 ≤ i ≤ m, 1 ≤ w_i ≤ 300), the i-th of them repesents at what second after the midnight the i-th ghost will come. All w_i's are distinct, they follow in the strictly increasing order.

Output

If it is possible to make at least r candles burn during each visit, then print the minimum number of candles that Anya needs to light for that.

If that is impossible, print  - 1.

Examples

Input

1 8 3
10

Output

3

Input

2 10 1
5 8

Output

1

Input

1 1 3
10

Output

-1

题意：晚上来了m个厉害的鬼，每个鬼来待一秒，来的时间是固定的，来的时候必须有r根蜡烛是亮的，否则主人公就挂了。主人公有无数根蜡烛，可以在任意时间点亮，每根持
续亮t秒，每次点亮需要1秒。问一晚上至少需要点亮几根蜡烛。
大题思路就是模拟，模拟的同时需要考虑最优，就是贪心思想。这道题思路通了写着就很顺了。（弱wa了11次。。。）

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<string.h>
using namespace std;
int time[310];//蜡烛点亮的时间
int w[310];
int main()
123
{
    int m, t, r;
    cin >> m >> t >> r;
    for (int i = 1; i <= m; i++)
    {
        scanf("%d", &w[i]);
    }
    if (t < r)
    {
        cout << "-1" << endl;
    }
    else
    {
        int ans = r;
        int start = w[1] - r;//最快灭的蜡烛点燃的时间
        for (int i = 1; i <= r; i++)
        {
            time[i] = start + i - 1;
        }
        for (int i = 2; i <= m; i++)
        {
            int num = 1;
            for (int j = 1; j <= r; j++)
            {
                if (time[j] + t < w[i])//蜡烛熄灭
                {
                    ans++;
                    time[j] = w[i] - num++;
                }
            }
        }
        cout << ans << endl;
    }
    return 0;
}