//#pragma GCC optimize ("Ofast")
//#pragma GCC optimize ("unroll-loops")
//#pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
#define pb push_back
#define F first
#define S second
#define ins insert
#define mp make_pair
#define fo(i, n1, n, x) for(int i = n1; i <= n; i += x)
#define foo(i, n, n1, x) for(int i = n; i >= n1; i -= x)
#define bit __builtin_popcount
#define md (l + ((r - l) / 2))
#define all(x) x.begin(),x.end()
#define eb emplace_back
#define ub upper_bound
#define lb lower_bound
#define ios ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define file(s) if (fopen(s".in", "r")) freopen(s".in", "r", stdin), freopen(s".out", "w", stdout)
*/
using namespace std;/*
using namespace __gnu_pbds;
using namespace __gnu_cxx;*/
using ll = long long;
#define int ll
const int N = 1e5 + 11;/*, mod = 1e9 + 7, mod2 = 998244353;
const int MAX = 1e5 + 11;
const int INF1 = 2e9 + 11;
const ll INF2 = 2e18 + 11;
const double INF3 = 1e8 + 11;
const int base = 500;
const int P = 31;
const int dx[] = {1, -1, 0, 0, 1, 1, -1, -1};
const int dy[] = {0, 0, 1, -1, 1, -1, 1, -1};
const double EPS = 1e-4;
const double PI = acos(-1.0);
template<typename T> using ordered_set = tree <T, null_type, less <T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T1, typename T2> inline void chmin(T1 &a, T2 b) { if (a > b) a = b; }
template<typename T1, typename T2> inline void chmax(T1 &a, T2 b) { if (a < b) a = b; }
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
typedef vector <int> vi;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
*/
int n, k, a[N];
main() {
// file("threesum");
// ios;
cin>>n>>k;
for (int i=1;i<=n;++i) cin>>a[i];
vector<int> v;
for (int i = 2; i <= n; ++i) v.push_back(a[i]-a[i-1]-1);
sort(v.begin(), v.end(),greater<int>());
int ans=0;
--k;
for (int i = k; i < v.size(); ++i) ans+=v[i];
cout<<ans+n;
cerr << "\nTime elapsed: " << (clock() + 0.0) / CLOCKS_PER_SEC;
return 0;
}
/**
1 3 6
*/
