#include "bits/stdc++.h"
#define endl '\n'
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<ll> vl;
typedef vector<int> vi;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<int>::iterator vit;
typedef set<int> si;
typedef map<int, int> mii;
void solve() {
ll n , k ,tmp;
cin >> n >> k;
vl a(n);
for ( ll i = 0 ; i< n ; i++){
cin >>a[i];
}
vl b(n-1);
for ( ll i = 0; i<n-1; i++){
b[i]= a[i+1] - a[i];
}
sort(all(b));
reverse(all(b));
ll ans = min((ll)a.size(),k);
for(ll i = k-1; i< n-1; i++){
ans += b[i];
}
cout << ans << endl;
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
unsigned long long ct = 1;
//cin >> ct;
while (ct--)
solve();
}
