#pragma GCC optimize("Ofast")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("fast-math")
#pragma GCC target("sse,sse2,sse3,ssse3,popcnt,abm,mmx,tune=native")
#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <stdio.h>
#include <cstdio>
#include <math.h>
#include <cmath>
#include <string>
#include <cstring>
#include <queue>
#include <deque>
#include <random>
#include <iomanip>
#include <bitset>
using namespace std;
template<typename T> void uin(T &a, T b) {
if (b < a) {
a = b;
}
}
template<typename T> void uax(T &a, T b) {
if (b > a) {
a = b;
}
}
#define int long long
#define left left228
#define right right228
#define prev prev228
#define list list228
#define mp make_pair
#define all(v) v.begin(), v.end()
#define forn(i, n) for (int i = 0; i < (int)n; ++i)
#define firn(i, n) for (int i = 1; i < (int)n; ++i)
#define x first
#define y second
const int N = 100 * 1000 + 228;
int t[N];
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, k;
cin >> n >> k;
uin(k, n);
for (int i = 1; i <= n; ++i) {
cin >> t[i];
}
sort(t + 1, t + n + 1);
vector<int> diff;
for (int i = 1; i < n; ++i) {
diff.push_back(t[i + 1] - t[i]);
}
sort(diff.rbegin(), diff.rend());
int res = k + t[n] - t[1];
for (int i = 0; i < k - 1; ++i) {
res -= diff[i];
}
cout << res << '\n';
return 0;
}
