#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ff first
#define ss second
#define all(a) a.begin(), a.end()
const int mod = 1e9 + 7;
const int N = 1e5;
signed main(){
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n, k; cin >> n >> k;
vector <int> a(n + 1);
for(int i = 1; i <= n; i ++) cin >> a[i];
priority_queue <int> q;
for(int i = 2; i <= n; i ++) q.push(a[i]-a[i-1]-1);
int dist = a[n]-a[1]+1;
k --;
while(q.size() && k --) {
int v = q.top();
q.pop();
dist -= v;
}
cout << dist;
return 0;
}
