#include <bits/stdc++.h>
//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,fma")
using namespace std;
#define ll long long
#define sped_up ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define rall(v) (v).rbegin(), (v).rend()
#define all(v) (v).begin(), (v).end()
#define pb push_back
#define S second
#define F first
const ll INF = (ll)1e9 + 1, INFL = (ll)1e18 + 1;
const ll mod = (ll)1e9 + 7, MAXN = (ll)2e5 + 1;
int main() {
sped_up;
ll n, k;
cin >> n >> k;
vector <ll> v;
ll first = 0;
ll last = 0, cnt = 0;
for (int i = 1; i <= n; i++) {
ll a;
cin >> a;
if (i == n) cnt += a + 1 - first;
if (i != 1) {
v.push_back(a - last - 1);
last = a;
}
else first = a;
}
k--;
sort(rall(v));
for (int i = 0; i < k; i++) cnt -= v[i];
cout << cnt;
}
