#include <bits/stdc++.h>
using namespace std;
#define ll long long
const ll mmod = 998244353;
#define vl vector<long long>
#define vll vector<vector<long long>>
#define pl pair<long long, long long>
#define vb vector<bool>
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
ll n, k;
cin >>n >> k;
vl nums(n);
for (ll i = 0; i < n; i++) cin >> nums[i];
vl gaps;
for (ll i = 0; i < n-1; i++){
gaps.push_back(nums[i+1]-nums[i]-1);
}
sort(gaps.begin(), gaps.end());
ll suma = n;
for (ll i = 0; i < n-k; i++){
suma += gaps[i];
}
cout << suma << "\n";
return 0;
}
