/*
,___________________________________________/7_
|-_______------. `\ |
_,/ | _______) |___\____________________________|
.__/`(( | _______ | (/))_______________=.
`~) \ | _______) | /----------------_/
`__y|______________| /
/ ________ __________/
/ /#####\( \ / ))
/ /#######|\ \( //
/ /########|.\______ad/`
/ /###(\)###||`------``
/ /##########||
/ /###########||
( (############||
\ \####(/)####))
\ \#########//
\ \#######//
`---|_|--`
((_))
`-`
*/
#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
#define Fast ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define bigint __int128
#define int long long
#define double long double
#define pii pair<int,int>
#define F first
#define S second
#define pb push_back
#define endl "\n"
#define stop(msg) {cout<<msg; return;}
#define stopp(msg, msg2) {cout<<msg<<msg2; return;}
#define all(aba) aba.begin(), aba.end()
#define rall(aba) aba.rbegin(), aba.rend()
#define take(aba) for (int abab=0; abab<aba.size(); abab++) cin>>aba[abab]
#define print(aba,sep) for (auto abab : aba) cout<<abab<<sep
#define pprint(aba,sep1,sep2) for (int abab=0; abab<aba.size(); abab++) cout<<aba[abab].F<<sep1<<aba[abab].S<<sep2
#define line "-------------------\n"
#define nline "\n-------------------\n"
#define linen "-------------------\n"
/// find_by_order (index), order_of_key (lower bound)
template<typename t>
using indexed_set = tree<t, null_type, less<t>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename t>
using indexed_multiset = tree<t, null_type, less_equal<t>, rb_tree_tag, tree_order_statistics_node_update>;
mt19937 rng(chrono::steady_clock().now().time_since_epoch().count());
int rand(int l, int r) {return rng()%(r-l+1)+l;}
double estimate_time(double n) {
double a = 7.1e-9, b = 0.02;
return max((double)0, a*n+b);
}
// O(1e8) = 1s.
const int MOD = (int)998244353;
const int N = (int)1005;
const int LG = (int)20;
const int INF = (int)4e18;
void solve(int cs){
int n,k; cin>>n>>k;
vector<int> a(n);
take(a);
vector<int> diff(n-1);
for (int i=0; i<n-1; i++) diff[i] = a[i+1] - a[i] - 1;
sort(all(diff));
int ans = n;
for (int i=0; i<n-k; i++) ans += diff[i];
cout<<ans<<endl;
}
signed main(){
//freopen("moocast.in", "r", stdin);
//freopen("moocast.out", "w", stdout);
Fast;
int t=1;
//cin>>t;
for (int i=1; i<=t; i++) {
solve(i);
}
return 0;
}
