#include <bits/stdc++.h>
#define int long long
#define float long double
#define pii pair<int, int>
#define tii tuple<int, int, int>
#define f first
#define s second
#define ve vector
#define emb emplace_back
#define em emplace
using namespace std;
const int inf = 1e18;
const int mod = 1e9 + 7;
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int n, k;
cin >> n >> k;
map<int, int> mp;
while (n--) {
int t;
cin >> t;
mp[t] = 1, mp[t+1] = max(mp[t+1], 0LL);
}
ve<pii> a;
int prev = -1;
for (auto &[x, y] : mp) {
if (prev == -1) prev = x;
if (y == 0) a.emb(prev, x), prev = -1;
}
ve<int> srt;
for (int i = 0; i < a.size()-1; i++) srt.emb(a[i+1].f-a[i].s);
sort(srt.rbegin(), srt.rend());
int sum = a.back().s - a[0].f;
for (int i = 0; i < min(k-1, (int)srt.size()); i++) sum -= srt[i];
cout << sum;
}
