//In the name of Allah
//Ya Ali!
#include <bits/stdc++.h>
using namespace std;
typedef long long ll ;
const ll maxn = 1000 * 1000 ;
const ll INF = 1e18 ;
#define f first
#define s second
ll n , k , a[maxn] ;
vector<ll> v ;
int main()
{
std::ios::sync_with_stdio(0) ;
cin.tie(0) ;
cout.tie(0) ;
cin >> n >> k ;
for(int i = 1 ; i <= n ; i ++){
cin >> a[i] ;
if(i > 1)v.push_back(a[i]-a[i-1]-1) ;
}
sort(v.begin( ) , v.end()) ;
ll sum = n ;
for(int i = 0 ; i < n-k ; i ++){
sum += v[i] ;
}
cout << sum ;
return 0;
}
/*
_ _ __
/_\ (_ (_) __)
/ \ _) . (_) (__
*/
