//Dost SEFEROĞLU
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair<int,int>
#define ff first
#define ss second
#define sp << " " <<
#define all(cont) cont.begin(),cont.end()
#define vi vector<int>
const int MOD = 1e9+7,inf = 2e18;
const int N = 1e5+50;
void solve() {
int n,k;
cin >> n >> k;
vi a(n+1);
for (int i=1;i<=n;i++) cin >> a[i];
int ans = inf;
int sm = a[n]-a[1];
vi diffs;
for (int i=2;i<=n;i++) diffs.push_back(a[i]-a[i-1]);
sort(all(diffs),greater<int>());
diffs.push_back(0);
for (int i=1;i<=k;i++) {
ans = min(ans,sm+i);
sm-=diffs[i-1];
}
cout << ans << endl;
}
signed main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#ifdef Dodi
freopen("in.txt","r",stdin);
freopen("out.txt","w",stdout);
#endif
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
