#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
typedef long long ll;
typedef pair<int, int> pii;
const int N = 1e5 + 3;
int n, k, a[N];
void solve() {
cin >> n >> k;
for (int i = 1; i <= n; ++i)
cin >> a[i];
vector<int> tmp;
int ans = a[n] - a[1];
for (int i = 1; i < n; ++i)
tmp.pb(a[i + 1] - a[i]);
sort(all(tmp), greater<int> ());
for (int i = 0; i < k - 1; ++i)
ans -= tmp[i];
cout << ans + k;
}
int main() {
cin.tie(NULL);
ios_base::sync_with_stdio(false);
solve();
return 0;
}
