/*
Editor: Abdelrahman Hossam
Nickname: Blobo2_Blobo2
IOI next year isA :)
*/
/*#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.2,popcnt,abm,mmx,avx2,tune=native")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-funroll-all-loops,-fpeel-loops,-funswitch-loops")*/
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define endl "\n"
#define all(v) v.begin(),v.end()
#define gen(arr,n,nxt) generate(arr,arr+n,nxt)
#define Blobo2_el_7akim_elly_3ayz_yro7_IOI_w_3ayz_yakol_jilaty ios_base::sync_with_stdio(false);cin.tie(0);
const int mo=1e9+7,INF=1e18;
int nxt(){int x;cin>>x;return x;}
signed main(){
Blobo2_el_7akim_elly_3ayz_yro7_IOI_w_3ayz_yakol_jilaty
int n=nxt(),k=nxt();
int arr[n];gen(arr,n,nxt);
int cnt=n;
int brr[n];
for(int i=0;i<n;i++)
brr[i]=arr[i]+1;
k-=n;
vector<int>v;
for(int i=0;i<n-1;i++)
v.push_back(abs(brr[i]-arr[i+1]));
sort(all(v));
for(int i=0;i<n&&k<0;i++){
cnt+=v[i];
k++;
}
cout<<cnt<<endl;
return 0;
}
