/*
written by sim_ple
*/
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define N 5009
#define itn int
#define all(x) x.begin() , x.end()
void solve(){
int n , k;
cin >> n >> k;
int a[n + 1];
for(int i = 1; i <= n; i++){
cin >> a[i];
}
vector<int> ans;
a[0] = 0;
for(int i = 2; i <= n; i++){
ans.push_back(a[i] - a[i - 1] - 1);
}
sort(all(ans));
int co = n;
for(int i = 0; i < n - k; i++){
co += ans[i];
}
cout << co << endl;
}
int32_t main() {
ios::sync_with_stdio(false);cin.tie(nullptr);
int t = 1;
//cin >> t;
while(t--) solve();
}
