// NAM MÔ A DI ĐÀ PHẬT
#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3","unroll-loops")
// defines
#define int long long
#define inf LLONG_MAX/20
#define fastio() ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define fr front
#define bk back
#define fi first
#define se second
// typedefs
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pi;
typedef pair<string, ll> psi;
typedef pair<ll, pi> pii;
typedef pair<pi, pi> piii;
signed main(){
fastio();
int n,k;
cin>>n>>k;
vector<int> v(n);
for(int i=0;i<n;i++) cin>>v[i];
vector<int> diff(n-1);
for(int i=0;i<n-1;i++) diff[i]=v[i+1]-v[i]-1;
sort(diff.begin(),diff.end());
int ans=0;
for(int i=0;i<n-k;i++) ans+=diff[i];
cout<<ans+n;
return 0;
}
