#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "/Library/debug/debug.h"
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
#define MAX 2e9
#define MIN -2e9
#define PI acos(-1.0)
#define mid(s, e) ((s) + ((e) - (s)) / 2)
#define clz(n) __builtin_clzll(n)
#define nbOfBits(n) __builtin_popcountll(n)
#define all(x) (x).begin(), (x).end()
#define endl '\n'
#define pb push_back
#define sz(a) static_cast<int>((a).size())
#define int long long
#define double long double
#define fi first
#define fill(n,arr) for(int i=1;i<=n;i++){ll x;cin>>x;arr.pb(x);}
#define se second
#define getunique(v) {sort(all(v)); v.erase(unique(all(v)), v.end());}
#define getorder(v) sort(all(v))
#define getlower(s) transform(s.begin(), s.end(), s.begin(), ::tolower)
#define getupper(s) transform(s.begin(), s.end(), s.begin(), ::toupper)
//#define reverse(s) reverse(s.begin(), s.end())
#define getmax(ans) *max_element(all(ans));
#define getmin(ans) *min_element(all(ans));
using ll = long long;
using vi = vector<int>;
using vc = vector<char>;
using vvc = vector<vc>;
using vvi = vector<vi>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vd = vector<double>;
using vvd = vector<vd>;
using vs = vector<string>;
using pii = pair<int, int>;
using pdd = pair<double, double>;
using vpii = vector<pii>;
using vpdd = vector<pdd>;
using si = set<int>;
using ssi = set<si>;
using sb = set<bool>;
using ssb = set<sb>;
using sd = set<double>;
using ssd = set<sd>;
using ss = set<string>;
using sc = set<char>;
// BEFORE coding are you sure you understood the statement correctly?
// PLEASE do not forget to read the sample explanation carefully.
// WATCH out for overflows & RTs in general.
// TEST your idea or code on the corner cases.
// ANALYZE each idea you have thoroughly.
const int dx[8]={0, 0, 1, -1, 1, -1, -1, 1};
const int dy[8]={1, -1, 0, 0, 1, -1, 1, -1};
int calculateLCM(int a, int b){return (a * b) / __gcd(a, b);}
const int MX = 1e7 + 1;
bool isPrime[MX];
void solve(){
int n,k;cin>>n>>k;
vi b(n);
for(int i=0;i<n;i++) cin>>b[i];
vi v(n - 1);
for(int i=1;i<n;i++){
v[i - 1] = b[i] - b[i - 1] - 1;
}
int ans = n;
sort(all(v));
for(int i=0;i<n - k;i++) ans += v[i];
cout<<ans<<endl;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
//int t;cin>>t;while(t--)
solve();
}
