//
// main.cpp
//
// Created by Panagiotis Chadjicostas on
// Copyright © Panagiotis Hadjicostas. All rights reserved.
//
#include <iostream>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <fstream>
#include <iomanip>
#include <iterator>
#include <limits>
#include <list>
#include <cstring>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <unordered_map>
using namespace std;
typedef int ll;
typedef vector<ll> vi;
typedef pair<ll,ll> ii;
#ifdef px
#define p(x) cerr<<#x<<' '<<x<<endl;
#else
#define p(x) {}
#endif
#define F first
#define S second
#define sz size
#define ls s,m,idx<<1
#define rs m+1,e,idx<<1|1
const ll MOD=ll(1e9)+7;
const ll MAXN=2*ll(1e6);
///////////////////////////////////////////////////////////////////////
void solve(){
ll n,k;cin>>n>>k;
vector<ll> a(n+1,ll());
for(ll i=1;i<=n;i++)cin>>a[i];
// logika fasi dp[i][x], eimai ston i kai xrisimopoio x stove
// dp [i] [x] = dp [i-1] [x-1] + 1
// dp [i] [x] = dp [i-1] [x] + a[i] - a[i-1] + 1;
// memory :?
/*
ll dp [n+2][k+2];
for(ll i=0;i<n+2;i++){
for(ll j=0;j<k+2;j++){
dp[i][j]=MOD;
}
}
dp[1][1]=1;
for(ll i=2;i<=n;i++){
for(ll x=1;x<=k;x++){
dp[i][x] = dp[i-1][x-1] + 1;
dp[i][x]=min(dp[i][x],dp[i-1][x]+a[i]-a[i-1]);
}
}
cout<<dp[n][k]<<endl;
*/
// pairno k mona tous + (n-k) mik diafores
ll ans=k;
priority_queue<ll,vi,greater<ll> > pq;
for(ll i=2;i<=n;i++){
pq.push(a[i]-a[i-1]);
}
for(ll i=1;i<=n-k;i++){
ans+=pq.top();
pq.pop();
}
cout<<ans<<endl;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll t=1;//cin>>t;
while (t--) {
solve();
}
return 0;
}
