//Expert Is Impossible For Me :(
#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define ll long long
#define ld long double
#define endl '\n'
#define pb push_back
#define pf push_front
#define speedyboy ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define bpc __builtin_popcount
#define all(x) x.begin() , x.end()
#define allr(x) x.rbegin() , x.rend()
#define F first
#define S second
#define pll pair<ll , ll>
#define turtle tuple<ll , ll , ll>
#define pss pair<string , string>
#define YES cout << "YES" << endl;
#define NO cout << "NO" << endl;
#define ordered_set tree<ll , null_type , less<ll> , rb_tree_tag , tree_order_statistics_node_update>
const ll sz = 1e6 + 5 , INF = 1e18 , MOD = 1e9 + 7;
ll a[sz];
ll mask , i , j , k;
void solve(){
ll n , m;
cin >> n >> m;
for(i = 1 ; i <= n ; i++) cin >> a[i];
ll ans = n;
if(m >= n){
cout << ans << endl;
return;
}
vector<ll> v;
for(i = 2 ; i <= n ; i++) v.pb(a[i] - a[i - 1] - 1);
sort(all(v));
for(i = 0 ; i < n - m ; i++) ans += v[i];
cout << ans << endl;
}
signed main(){
speedyboy;
//open;
ll t = 1;
//cin >> t;
while(t--){
solve();
}
}
