#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <fstream>
#include <cassert>
#include <cstring>
#include <numeric>
#include <ctime>
#include <complex>
#include <bitset>
#include <random>
#include <climits>
#include <stack>
#pragma GCC optimize("Ofast")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.1,sse4.2,popcnt,abm,mmx,avx,avx2,tune=native")
using namespace std;
typedef long long ll;
typedef long double ld;
#define int ll
#define double ld
#define loop(i, n) for(int i = 0; i < (int)n; ++i)
#define loop1(i, n) for(int i = 1; i <= (int)n; ++i)
#define F first
#define S second
#define pb push_back
#define pi pair <int, int>
#define all(x) begin(x), end(x)
#define ti tuple <int, int, int>
#define Point Vect
#define no {cout << -1; return;}
#define yes {cout << "Yes"; return;}
#define mkp make_pair
#define mkt make_tuple
#define cerr if(0) cerr
void solve() {
int n, k;
cin >> n >> k;
vector <int> dist(n);
int lst;
loop(i, n) {
int t; cin >> t;
if (i)
dist.pb(t - lst - 1);
lst = t;
}
sort(all(dist));
k = min(k - 1, (int)dist.size());
loop(i, k)
dist.pop_back();
int ans = n;
for (int d : dist)
ans += d;
cout << ans;
}
signed main() {
//freopen("b2.txt", "r", stdin);
//freopen("ans9.txt", "w", stdout);
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
//int t; cin >> t; loop(i, t)
solve();
return 0;
}
