// In the name of God
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pii;
typedef pair<ll, ll> pll;
#define pb push_back
#define S second
#define F first
#define mp make_pair
#define smax(x, y) (x) = max((x), (y))
#define smin(x, y) (x) = min((x), (y))
#define all(x) (x).begin(), (x).end()
#define len(x) ((ll)(x).size())
const int maxn = 1e5 + 5;
const int inf = 1e9 + 7;
int n, k, a[maxn];
int32_t main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> k;
for(int i = 0; i < n; i++) cin >> a[i];
vector<int> vec;
for(int i = 1; i < n; i++) vec.pb(a[i] - a[i - 1] - 1);
sort(all(vec));
int ans = n;
for(int i = 0; i < n - k; i++) ans += vec[i];
cout << ans << '\n';
return 0;
}
