/***********************************
██╗░░██╗████████╗██╗░░░░░███╗░░░███╗
██║░░██║╚══██╔══╝██║░░░░░████╗░████║
███████║░░░██║░░░██║░░░░░██╔████╔██║
██╔══██║░░░██║░░░██║░░░░░██║╚██╔╝██║
██║░░██║░░░██║░░░███████╗██║░╚═╝░██║
╚═╝░░╚═╝░░░╚═╝░░░╚══════╝╚═╝░░░░░╚═╝
***********************************/
//#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#include <unistd.h>
//#include "functions.h"
#define int l
#define f first
#define s second
#define endl '\n'
#define l long long
#define ara <<" "<<
#define pb push_back
#define pairs pair<l,l>
#define NO cout<<"NO"<<endl
#define stop system("pause")
#define YES cout<<"YES"<<endl
#define all(v) v.begin(),v.end()
#define yesno(v) ((v) ? "YES" : "NO")
#define dbg(x) cout<<#x<<" = "<<x<<endl;
#define filereader() ifstream cin(input);
#define fileprinter() ofstream cout(output);
#define fast ios_base::sync_with_stdio(NULL);cin.tie(NULL);cout.tie(NULL);
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less_equal<int> , rb_tree_tag, tree_order_statistics_node_update> indexed_set;
const l N = 2e5 + 5;
const l INF = 1e18;
const l mod = 1e9 + 7;
const string input = "input.txt";
const string output = "output.txt";
l gcd(l a, l b){
if(b == 0){
return a;
}
return gcd(b,a%b);
}
l binpow(l a, l b) {
if (b == 0)
return 1;
l res = binpow(a, b / 2);
if (b % 2)
return ((res * res) % mod * a) % mod;
else
return (res * res) % mod;
}
void solve(){
l n,k;
cin>>n>>k;
l a[n];k--;
for(int i = 0 ; i < n ; i++){
cin>>a[i];
}
vector<l>v;
l sum = 0;
for(int i = 0 ; i < n - 1 ; i++){
v.pb(a[i+1] - a[i] - 1);
sum += a[i+1] - a[i] - 1;
}
sort(all(v));
reverse(all(v));
for(int i = 0 ; i < k ; i++ ){
sum -= v[i];
}
cout<<sum + n;
}
signed main(){
//fast;
//srand(time(NULL));
//system("color a");
//const char* color = "color" + to_string(rand() % 10);
l n = 1;
//cin>>n;
while(n--){
solve();
}
}
