#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define pb(e) push_back(e)
#define sv(a) sort(a.begin(),a.end())
#define sa(a,n) sort(a,a+n)
#define mp(a,b) make_pair(a,b)
#define vf first
#define vs second
#define ar array
#define all(x) x.begin(),x.end()
const int inf = 0x3f3f3f3f;
const int mod = 1000000007;
const double PI=3.14159265358979323846264338327950288419716939937510582097494459230;
bool remender(ll a , ll b){return a%b;}
void solve(){
int n;
cin >> n;
int k;
cin >> k;
ll arr[n];
vector<ll> dif;
for(int i = 0; i < n; i++)cin >> arr[i];
for(int i = 1; i < n; i++)dif.pb(arr[i] - (arr[i-1] + 1) );
sv(dif);
reverse(all(dif));
ll ans = n;
for(int i = 0; i < n-1; i++){
if(i >= k-1)ans += dif[i];
}
cout << ans << '\n';
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
//int t;cin >> t;while(t--)
solve();
return 0;
}
