#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC optimize("-Ofast")
#include <bits/stdc++.h>
#include <algorithm>
#include <iostream>
#include <vector>
#include <limits>
#include <cmath>
#include <stack>
#include <queue>
#include <map>
#include <math.h>
using namespace std;
using ll = long long;
void solve(){
ll n, k;
cin >> n >> k;
if(n == 1){
cout << 1 << endl;
return;
}
vector<ll> list_n(n, 0);
for(ll i = 0; i < n; i++){
cin >> list_n[i];
}
vector<ll> diff(n - 1, 0);
for(ll i = 0; i < n - 1; i++){
diff[i] = list_n[i + 1] - list_n[i];
}
sort(diff.begin(), diff.end());
ll total = n;
for(ll i = 0; i < n - k; i++){
total += diff[i] - 1;
}
cout << total;
}
int main(){
ios_base::sync_with_stdio(false);
cout.tie(0);
cin.tie(0);
ll t = 1;
while(t--){
solve();
}
}
