#include<bits/stdc++.h>
using namespace std;
#define debug(x) cout << '[' << #x << " is: " << x << "] " << '\n';
#define imod(a , n) (a % n + n ) % n
#define fastio ios_base::sync_with_stdio(false);cin.tie(0);
#define inF freopen("milkvisits.in","r",stdin );
#define outF freopen("milkvisits.out" , "w" , stdout ) ;
#define sor(v) sort(v.begin() , v.end());
#define print(v) for(auto f : v ) cout << f << " " ;
#define rsor(v) sort(v.rbegin() , v.rend());
#define rev(v) reverse(v.begin() , v.end());
#define lp(i , n) for(int x = i ; x < n ; x ++)
#define ll long long
#define read(arr , x , n) for(int i = x ; i < n ; i ++ )cin >> arr[i];
const double eps = 1e-6 , PI = acos(-1) ;
const long long OO = 1e18 ;
const ll N = 22 , oo = 1e9 + 1 , M = 2000002, mod = 1e9 + 7 , K = 12;
// +_+
int32_t main(){
// inF;outF;
fastio;
// Dont Forget memset
int n , k ;
cin >> n >> k ;
vector<int>v(n);
for(auto &it : v)
cin >> it ;
sor(v);
ll ans = v[n - 1] + 1 - v[0];
vector<int>V;
for(int i = 1 ; i < n ; i ++)V.push_back(v[i] - v[i - 1] - 1);
rsor(V);
for(int i = 0 ; i < k - 1 ; i++)
ans -= V[i];
cout << ans ;
}
