在线IDE中输出为22，但#4测试点下载数据输出是20，求助QwQ 源代码如下：

#include<bits/stdc++.h>
using namespace std;
int m, s, c, l = 0;
int cha[10001],a[10001];
bool cmp(int a,int b)
{
    return a > b;
}
int main()
{
    cin >> m >> s >> c;
    if (m > c)
    {
        cout << c;
        return 0;
    }
    for (int i = 0; i < c;++i)
    {
        cin >> a[i];
    }
    sort(a, a+c);
    l = a[c - 1] - a[0]+1;
    for (int i = 1; i < c;++i)
    {
        cha[i] = a[i] - a[i - 1];
    }
    sort(cha, cha + c-1, cmp);
    for (int i = 1; i <= m-1;++i)
    {
        l = l-cha[i-1] + 1;
    }
    cout << l;
    return 0;
}