#include<bits/stdc++.h>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
const ll maxn=200005;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int n,k;
cin >> n >> k;
int a[n+1];
for (int i=1; i<=n; i++) {
cin >> a[i];
}
priority_queue<int,vector<int>,greater<int>>pq;
for (int i=1; i<n; i++) {
pq.push((a[i+1])-(a[i]+1));
}
int cnt=n;
int ans=n;
if (k>=cnt) {
cout << ans;
} else {
for (int i=1; i<=cnt-k; i++) {
if (!pq.empty()) {
int u=pq.top();
pq.pop();
ans+=u;
}
}
cout << ans;
}
}
