#include "bits/stdc++.h"
#define FAST ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define ff first
#define ss second
#define ll long long
using namespace std;
int main()
{
FAST;
int n, k; cin >> n >> k;
vector < int > v(n);
for(int i = 0; i < n; i++) cin >> v[i];
vector < int > p;
for(int i = 1; i < n; i++) p.push_back(v[i] - v[i - 1] - 1);
sort(begin(p), end(p), greater < int > ());
int ans = v[n - 1] - v[0] + 1;
for(int i = 0; i < k - 1; i++) ans -= p[i];
cout << ans << "\n";
return 0;
}
