Fixing

/*
    Task    : _example
    Author  : Phumipat C. [MAGCARI]
    Language: C++
    Created : 17 October 2022 [21:11]
*/
#include <bits/stdc++.h>
using namespace std;
int a[100010];
priority_queue<int > heap;
int main()
{
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    int n,m,k;
    cin >> n >> m >> k;
    for(int i=1;i<=m;i++)
        cin >> a[i];
    int ans = (a[1]-1) + (n-a[m]);
    for(int i=2;i<=m;i++){
        if(a[i]-a[i-1]-1 == 0)  continue;
        heap.push(a[i]-a[i-1]-1);
    }
    k--;
    while(k-- && !heap.empty()){
        ans+=heap.top();
        heap.pop();
    }
    cout << n-ans-m << '\n';
    return 0;
}