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#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <cmath>
#include <iomanip>
#include <stack>
#include <map>
#include <queue>
#include <cstring>
#include <string>
#include <tuple>
#include <utility>
#define ll long long
#define endl "\n"
#define ld long double
#define db double
#define rt return 0
#define FAST ios::sync_with_stdio(false);cin.tie(nullptr)
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define V vector
#define pii pair<int,int>
#define pll pair<ll,ll>
#define D2 vector<vector<int>>
#define pq priority_queue
#define frop freopen("676776","r",stdin);freopen("676776","w",stdout);
#define itn int
#define tin int
#define pss pair<string,string>
#define all(x) x.begin(),x.end()
using namespace std;
ll gcd(ll a, ll b)
{
if (a == 0 || b == 0) {
return max(a, b);
}
if (a <= b) {
return gcd(a, b % a);
}
else {
return gcd(a % b, b);
}
}
const int ans = 1e9 + 7;
int main() {
FAST;
int n, k;
cin >> n >> k;
vector<ll>a(n);
for (int i = 0; i < n; i++) {
cin >> a[i];
}
ll ans = a[n - 1] - a[0] + 1;
vector<ll>tarb;
for (int i = 1; i < n; i++) {
tarb.pb(a[i] - a[i - 1] - 1);
}
sort(tarb.rbegin(), tarb.rend());
for (int i = 0; i < min(k - 1, (int)tarb.size()); i++) {
ans -= tarb[i];
}
cout << ans << endl;
rt;
}
