#include <bits/stdc++.h>
using namespace std;
#define overload4(a, b, c, d, name, ...) name
#define rep1(i, n) for(ll i = 0; i < (n); ++i)
#define rep2(i, a, b) for(ll i = (a); i < (b); ++i)
#define rep3(i, a, b, c) for(ll i = (a); i < (b); i += (c))
#define rep(...) overload4(__VA_ARGS__, rep3, rep2, rep1)(__VA_ARGS__)
#define per1(i, n) for(ll i = (n) - 1; i >= 0; --i)
#define per2(i, a, b) for(ll i = (b) - 1; i >= a; --i)
#define per3(i, a, b, c) for(ll i = (b) - 1; i >= (a); i -= (c))
#define per(...) overload4(__VA_ARGS__, per3, per2, per1)(__VA_ARGS__)
#define pb emplace_back
#define lb(v,k) (ll) (lower_bound(all(v), (k)) - v.begin())
#define ub(v,k) (ll) (upper_bound(all(v), (k)) - v.begin())
#define all(a) a.begin(),a.end()
#define fi first
#define se second
#define PQ(T) priority_queue<T>
#define SPQ(T) priority_queue<T, vector<T>, greater<T>>
typedef long long ll;
typedef pair<ll,ll> P;
using vi = vector<ll>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;
using vp = vector<P>;
using vvp = vector<vp>;
constexpr int _ = 100010;
ll t[_], d[_];
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
ll n, k; cin >> n >> k;
rep(i, n) cin >> t[i];
rep(i, n - 1) d[i] = t[i + 1] - t[i] - 1;
sort(d, d + n - 1); reverse(d, d + n - 1);
ll ans = t[n - 1] - t[0] + 1;
rep(i, k - 1) ans -= d[i];
cout << ans << '\n';
return 0;
}
