//apig's property
//Happiness can be found, even in the darkest of times, if one only remembers to turn on the light
//El Pueblo Unido Jamas Sera Vencido
//The saddest thing about betrayal? is that it never comes from your enemies
//Do or do not... there is no try
#include<bits/stdc++.h>
#define fast ios_base::sync_with_stdio(0) , cin.tie(0) , cout.tie(0)
#define F first
#define S second
#define pb push_back
#define vll vector< ll >
#define vi vector< int >
#define pll pair< ll , ll >
#define pi pair< int , int >
#define all(s) s.begin() , s.end()
#define sz(s) s.size()
#define str string
#define md ((s + e) / 2)
#define mid ((l + r) / 2)
#define msdp(dp) memset(dp , -1 , sizeof dp)
#define mscl(dp) memset(dp , 0 , sizeof dp)
#define C continue
#define R return
#define B break
#define lx node * 2
#define rx node * 2 + 1
using namespace std;
typedef long long ll;
ll q, dp[105][100005], a[555555] , b[555555], k, l, m, n, o, p;
map < char , ll > mp;
vll adj[555555];
const ll mod = 1e9+7;
str s;
void solve(){
cin >> n >> k;
for(ll i = 1 ; i <= n ; i++){
cin >> a[i] ;
}
sort(a + 1 , a + n + 1) ;
vll v ;
for(ll i = 2 ; i <= n ; i++){
v.pb(a[i] - a[i - 1] - 1) ;
}
sort(all(v)) ;
reverse(all(v)) ;
o = 0 ;
for(ll i = 1 ; i < k ; i++)o += v[i - 1] ;
cout << a[n] - a[1] + 1 - o << endl;
}
int main(){
fast ;
//cin >> q;
q = 1;
while(q--){
solve();
}
}
