#include <iostream>
#include <vector>
#include <assert.h>
#include <random>
#include <chrono>
#include <iomanip>
#include <algorithm>
#include <set>
#include <queue>
#include <unordered_set>
using namespace std;
#define endl "\n"
#define ll long long
const ll inf = 1e9 + 69;
const int MX = 5e5 + 5;
const int LG = (int)log2(MX);
const ll mod = 1e9 + 7;
const int BLOCK = 450;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int main(){
int n, k;
cin >> n >> k;
vector<int> v(n);
for(int i = 0; i < n; i ++)
cin >> v[i];
vector<int> len(n - 1);
for(int i = 0; i < n - 1; i ++)
len[i] = v[i + 1] - v[i] - 1;
sort(len.begin(), len.end());
int ans = n;
for(int i = 0; i < n - k; i ++)
ans += len[i];
cout << ans << endl;
}
