#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
#define pb push_back
#define pii pair<int, int>
#define pll pair<ll, ll>
#define st first
#define nd second
#define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
#define debug false
const int MAXN = 100 * 1000;
ll a[MAXN];
vector<ll> v;
int main () {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n, k;
cin >> n >> k;
ll wyn = n;
for (int i = 0; i < n; i ++) {
cin >> a[i];
}
for (int i = 1; i < n; i ++) {
v.pb(a[i] - a[i - 1] - 1);
}
sort(v.begin(), v.end());
for (int i = 0; i < n - k; i ++) {
wyn += v[i];
}
cout << wyn << "\n";
return 0;
}
