#include <bits/stdc++.h>
#define ll long long int
#define mp make_pair
#define pb push_back
#define ld long double
#define pii pair<int,int>
#define sz(x) (int)x.size()
#define piii pair<pii,pii>
#define precise cout<<fixed<<setprecision(10)
#define st first
#define nd second
#define ins insert
#define vi vector<int>
#define BOOST ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
using namespace std;
const int MAX=1e5+5;
const int inf=1e9+9;
int tab[MAX];
ll ans=0;
vi diff;
int32_t main()
{
BOOST;
int n,k;
cin>>n>>k;
int mini=inf,maxi=-inf;
for (int i=1;i<=n;i++)cin>>tab[i],mini=min(mini,tab[i]),maxi=max(maxi,tab[i]);
ans=maxi-mini+1;
for (int i=2;i<=n;i++)diff.pb(tab[i]-tab[i-1]-1);
sort(diff.begin(),diff.end(),greater<int>());
k--;
for (int i=0;i<k;i++)ans-=diff[i];
cout<<ans;
return 0;
}
