// include
#include<bits/stdc++.h>
using namespace std;
// random
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
// templates
template<class X, class Y>
bool maximize(X &x, const Y &y) {
if (y > x) {
x = y;
return (true);
} else return (false);
}
template<class X, class Y>
bool minimize(X &x, const Y &y) {
if (y < x) {
x = y;
return (true);
} else return (false);
}
// define
#define fi first
#define se second
#define pub push_back
#define pob pop_back
#define puf push_front
#define pof pop_front
#define eb emplace_back
#define upb upper_bound
#define lwb lower_bound
#define left VAN
#define right TAN
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).begin(),(a).end()
#define sort_and_unique(a) sort(all(a));(a).resize(unique(all(a))-a.begin())
// another define
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
// limit
const int oo = 2e9;
void solve() {
int n, k;
cin >> n >> k;
vector<int> t(n);
for (int i = 0; i < n; i++) cin >> t[i];
int ans = t[n - 1] - t[0] + 1;
vector<int> v;
for (int i = 0; i < n - 1; i++)
v.pub(t[i + 1] - t[i] - 1);
sort(v.begin(), v.end(), greater<int>());
for (int i = 0; i < k - 1; i++)
ans -= v[i];
cout << ans;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int t = 1;
//cin >> t;
while (t--) solve();
return 0;
}
