#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define lld double
#define int ll
#define usaco(fname) freopen(#fname ".in","r",stdin);freopen(#fname ".out","w",stdout);
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { os << '{'; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << '}'; }
// const ll INF = 1e18;
const int INF = 1e9;
const int mod = 1e9+7;
const lld PI = acos(-1.0);
int di[] = {1, -1, 0, 0, 1, 1, -1, -1};
int dj[] = {0, 0, 1, -1, 1, -1, 1, -1};
#define debug(x) cout << #x << ": " << x << endl;
#define add(a, b) a += b, a %= mod
#define mul(a, b) ((a % mod) * (b % mod)) % mod
#define all(x) x.begin(),x.end()
void solve() {
int n,k;cin>>n>>k;
// delete n-k-1 largest
vector<int> a(n), deltas;
for (int i = 0; i < n; i++) cin >> a[i];
for (int i = 0; i+1 < n; i++) deltas.push_back(a[i+1] - a[i]-1);
sort(all(deltas));reverse(all(deltas));
// cout << deltas << endl;
int ans = a.back() - a.front() + 1;
int ops = max(0ll, k-1);
// debug(ops);
for (int i = 0; i < ops; i++) ans -= deltas[i];
cout << ans << endl;
}
int32_t main() {
ios_base::sync_with_stdio(0);cin.tie(0);
int t=1;
while(t--) solve();
return 0;
}
