//#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, m, a[N];
main() {
file("threesum");
ios;
cin>>n>>m ;
long long l = 0 , t;
vector<long long > v;
for(int i = 0 ; i<n ; i++)
{
cin>>t;
if(i)
{
v.push_back( t - l -1 );
}
l = t;
}
long long k = 0;
sort(v.begin() , v.end());
for(int i = 0;i<n - m ;i++)
k+=v[i];
cout<< n+k;
cerr << "\nTime elapsed: " << (clock() + 0.0) / CLOCKS_PER_SEC;
return 0;
}
/**
1 3 6
*/
