#include <bits/stdc++.h>
using namespace std;
 
#define fi first
#define se second
#define pb push_back
using vi = vector <int>;
using ll = long long;
using pii = pair <int, int>;
//~ const ll mod = 998244353;
const ll mod = 1e9 + 7;
ll qpow(ll a, ll b, ll m = mod) { ll r = 1, t = a;
	for(; b; b /= 2) { if(b & 1) r = r * t % m; t = t * t % m; } return r; }

const int N = 2e5 + 11;
ll a[N], b[N];

int main() {
	ios :: sync_with_stdio(false);
	int n, k; cin >> n >> k;
	for(int i = 0; i < n; i ++)
		cin >> a[i];
	sort(a, a + n);
	for(int i = 0; i < n - 1; i ++)
		b[i] = a[i + 1] - a[i];
	sort(b, b + n - 1);
	reverse(b, b + n - 1);
	
	ll ans = a[n - 1] - a[0];
	ans -= accumulate(b, b + k - 1, 0LL);
	cout << ans << '\n';
}