#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
typedef long long ll;
using namespace __gnu_pbds;
#define endl '\n'
#define hitaf ios_base::sync_with_stdio(false); cin.tie(0);
#define fi first
#define se second
template <typename T>
using ordered_set = tree<T,null_type,less<T>,rb_tree_tag, tree_order_statistics_node_update>;
const ll MOD = 1e9 + 7;
const ll MOD1 = 998244353;
const ll INF = 4500000000000000000LL;
const ll mod1 = 6900000469;
const ll mod2 = 698000002369;
ll n, m, q, k, a[500005], b[500005], c[500005];
string s;
vector<ll> adj[200005];
int main(){
hitaf
int T = 1;
// cin >> T;
while(T--){
cin >> n >> k;
priority_queue<ll> pq;
for(int i = 1; i <= n; i++) cin >> a[i];
ll ans = a[n] - a[1] + 1;
for(int i = 2; i <= n; i++) pq.push(a[i] - a[i - 1] - 1);
ll seg = 1;
while(seg < k){
ans -= pq.top();
pq.pop();
seg++;
}
cout << ans << endl;
}
return 0;
}
/*
1 2 2 3 = 6
3 5 = 6;
*/
