#include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <iomanip>
#include <vector>
#include <map>
#include <stack>
#include <queue>
using namespace std;
#define ll long long
#define pb push_back
#define el '\n'
#define mpair make_pair
#define MASK(i) (1LL << (i))
#define BIT(mask, i) (((mask) >> (i)) & 1)
#define fi first
#define se second
/* Author: Pham Gia Phuoc */
const int MOD = (int)(1e9) + 7;
template <class T1, class T2>
void add(T1 &a, T2 b){
a += b;
if(a >= MOD) a -= MOD;
}
template <class T1, class T2>
void sub(T1 &a, T2 b){
a -= b;
if(a < 0) a += MOD;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if(a > b){a = b; return true;} return false;
}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if(a < b){a = b; return true;} return false;
}
/** END OF TEMPLATE. DRINK A CUP OF COFFEE BEFORE READING MY CODE **/
const int MAX = 100010;
const ll INF = (ll) 1e18 + 67LL;
const int oo = (int)(1e9 + 7);
const int NUM_BIT = 62;
int N, K, t[MAX];
void init(){
cin >> N >> K;
for(int i = 1; i <= N; i++) cin >> t[i];
}
bool checkSubtask1(){
if(N > 20) return false;
for(int i = 1; i <= N; i++) if(t[i] > 20) return false;
return true;
}
ll solveSubtask1(){
ll ans = INF;
for(int mask = 0; mask < MASK(N); mask++) if(__builtin_popcount(mask) <= K - 1) {
ll cur = 0;
int pre = 1;
for(int i = 2; i <= N; i++) if(BIT(mask, i - 1)) {
cur += (t[i - 1] + 1 - t[pre]);
pre = i;
}
cur += (t[N] + 1 - t[pre]);
minimize(ans, cur);
}
// cout << ans << el;
return ans;
}
ll solveSubtask3(){
ll ans = t[N] - t[1] + 1;
vector <ll> b;
for(int i = 1; i < N; i++) b.push_back(1LL * (t[i + 1] - (t[i] + 1)));
sort(b.begin(), b.end(), greater <ll>());
// for(int i = 0; i < b.size(); i++) cout << b[i] << ' ';
if(K > 1){
for(int i = 0; i < K - 1; i++){
ans -= b[i];
}
}
return ans;
}
void gen(){
N = 10; K = 2;
for(int i = 1; i <= N; i++) t[i] = rand() % 1000;
sort(t + 1, t + N + 1);
}
void solve(){
// if(checkSubtask1()){solveSubtask1(); return;}
// solveSubtask3();
// ll fi = solveSubtask1();
// ll se = solveSubtask3();
// // ll se;
// if(fi != se){
// cout << "WA" << el;
// for(int i = 1; i <= N; i++) cout << t[i] << ' ';
// }
// else cout << "AC" << el;
// cout << solveSubtask1() << el << solveSubtask3() << el;
// solveSubtask3();
// cout << el;
cout << solveSubtask3() << el;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define test "test"
srand(time(0));
int t = 1;
while(t--){
// gen();
init();
solve();
}
return 0;
}
/*** ROAD TO VOI 2024 ***/
