#include<bits/stdc++.h>
using namespace std;
int n,m,k,s,t,tot,now,ans,M,S,C,a[2001],b[2000];
int main()
{
    cin>>M>>S>>C;
    if(M>=C)
    {
        cout<<C;
        return 0;
    }
    for(int i=1;i<=C;i+=1)cin>>a[i];
    sort(a+1,a+C+1);
    ans=a[C]-a[1]+1;
    for(int i=1;i<C;i+=1)b[i]=a[i+1]-a[i]-1;
    sort(b+1,b+C);
    for(int i=1;i<=M-1;i+=1)ans-=b[C-i];
    cout<<ans<<endl;
}

$AC$ $Code$:

#include <bits/stdc++.h> 
using namespace std;
long long m, s, c, a[205], b[205], ans;
int main()
{
    freopen("修理牛棚.in", "r", stdin);
    freopen("修理牛棚.out", "w", stdout);
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> m >> s >> c;
    for (int i = 1; i <= c; i++)
        cin >> a[i];
    sort(a + 1, a + c + 1);
    ans = a[c] - a[1] + 1;
    for (int i = 1; i <= c - 1; i++)
        b[i] = a[i + 1] - a[i] - 1;
    sort(b + 1, b + c);
    for (int i = c - 1; i >= c - m + 1; i--)
        ans -= b[i];
    cout << ans << endl;
    return 0;
}