#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <fstream>
#include <sstream>
#include<set>
#include<stack>
#include<time.h>
#include <sys/types.h>
#include <tuple>
#include <numeric>
#include <iterator>
#include <atcoder/all>

#include <bits/stdc++.h>


#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace atcoder;
using namespace std;
typedef long long int ll;
typedef modint1000000007 mint;




ll gcd(ll a, ll b) {
    if (a < b)swap(a, b);
    if (b == 0)return a;

    return gcd(b, a % b);
}
int lcm(int a, int b) {
    return a * b / gcd(a, b);
}

/*
解説動画参考
解説ブログ参考
https://yukicoder.me/problems/no/615/editorial

*/




int main()
{

    int Q;
    Q = 1;
    //cin >> Q;   

    
    while (Q--) {
        int n;
        cin >> n;
        int k;
        cin >> k;
        vector<ll>p(n);
        for (int i = 0; i < n; i++) {
            cin >> p[i];
            
        }
        sort(p.rbegin(), p.rend());
        vector <ll>x;
        for (int i = 0; i < n-1; i++) {
            x.emplace_back(p[i] - p[i + 1]);
        }
        sort(x.begin(), x.end());
        ll t = 0;
        for (int i = 0; i < n - k; i++)t += x[i];
        cout << t << endl;
        

    }

    return 0;
}