//tavakol bar khoda
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
const int MAXN = (int)1e5 + 7;
const int MOD = (int)1e9 + 7;
const int infint = (int)1e8 + 3;
const ll inf = (ll)1e18;
int n, k, a[MAXN];
int main()
{
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cin >> n >> k;
for (int i = 0; i < n; i++)
cin >> a[i];
a[n] = a[n - 1];
ll ans = k + a[n] - a[0];
vector<ll> v;
for (int i = 0; i < n; i++)
v.push_back(a[i] - a[i + 1]);
sort(v.begin(), v.end());
for (int i = 0; i < k - 1; i++)
ans += v[i];
cout << ans;
}
