#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> PII;

const int MM = 1e9 + 7;
const double eps = 1e-8;
const int MAXN = 2e6 + 10;

int n, m;

void prework(){

}

void read(){

}

ll a[MAXN];
int k;

void solve(int casi){
//	cout << "Case #" << casi << ": ";
	cin >> n >> k;
	for (int i = 1; i <= n; i++)
		cin >> a[i];
	sort(a + 1, a + n + 1);
	for (int i = 1; i < n; i++)
		a[i] = a[i+1] - a[i];
	sort(a + 1, a + n);
	ll ans = 0;
	for (int i = 1; i < n; i++)
		ans += a[i];
	for (int i = 1; i <= k - 1; i++){
		ans -= a[n - i];
	}
	cout << ans << endl;
}

void printans(){

}

int main(){
	std::ios::sync_with_stdio(false);
	prework();
	int T = 1;
//	cin>>T;
	for(int i = 1; i <= T; i++){
		read();
		solve(i);
		printans();
	}
	return 0;
}