#include <iostream>
#include <fstream>
#include <iomanip>
#include <vector>
#include <set>
#include <map>
#include <cstring>
#include <string>
#include <cmath>
#include <cassert>
#include <ctime>
#include <algorithm>
#include <sstream>
#include <list>
#include <queue>
#include <deque>
#include <numeric>
#include <stack>
#include <cstdlib>
#include <cstdio>
#include <iterator>
#include <functional>
#include <unordered_set>
#include <unordered_map>
#include <stdio.h>
#include <bitset>
#include <cstdint>
#include <cassert>
#include <complex>
#include <climits>
#include <random>
using namespace std;
#define ll long long
#define pb push_back
#define ull unsigned long long
#define F first
#define S second
#define all(v) v.begin(), v.end()
#define rall(x) x.rbegin(), (x).rend()
const ll mod = 1e9 + 7;
const int block = 450;
const ll LINF = 1e16;
const int INF = 1e8;
ll add(ll a, ll b){
ll x = a + b;
if(x < 0) x += mod;
if(x >= mod) x -= mod;
return x;
}
ll mul(ll a, ll b){
return (a * b) % mod;
}
ll sub(ll x, ll y){
return add(x, -y);
}
ll binpow(ll a, ll b) {
ll res = 1LL;
while (b > 0) {
if (b & 1)
res = (res * a) % mod;
a = (a * a) % mod;
b >>= 1;
}
return res;
}
int n, m;
int a[5005];
void solve(){
cin >> n >> m;
int ans = 0;
for(int i = 1; i <= n; i++){
cin >> a[i];
}
sort(a + 1, a + 1 + n);
ans = (a[n] + 1) - a[1];
vector<int> v;
int prev = a[1] + 1;
for(int i = 2; i <= n; i++){
v.pb(-(a[i] - prev));
prev = a[i] + 1;
}
sort(all(v));
for(int i = 0; i < min((int) v.size(), (m - 1)); i++){
int x = v[i];
ans += x;
}
cout << ans;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL), cout.tie(NULL);
int xach = 1;
//cin >> xach;
while(xach--) solve();
}
