#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
#define pb push_back
#define mp make_pair
#define all(v) (v).begin(),(v).end()
#define sz(v) int((v).size())
#define do_not_disturb ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl '\n'
int mod = 1e9+7;
ll modulo(ll a) {
return ((a % mod) + mod) % mod;
}
ll add(ll a, ll b) {
return modulo(a + b);
}
ll mult(ll a, ll b) {
return modulo(a * b);
}
ll binpow(ll a, ll b) {
ll res = 1;
while (b) {
if (b&1) {
res = mult(res, a);
}
a = mult(a, a);
b >>= 1;
}
return res;
}
void solve() {
int n, k;
cin >> n >> k;
vector <int> v(n);
for (auto &to : v) cin >> to;
vector <int> diff;
for (int i = 0; i < n-1; i++) {
diff.pb(v[i+1]-v[i]-1);
}
sort(all(diff));
int ans = v.back()-v[0]+1;
while (k > 1) {
k--;
ans -= diff.back();
diff.pop_back();
}
cout << ans;
}
int main() {
do_not_disturb
int t = 1;
//~ cin >> t;
while (t--) {
solve();
}
return 0;
}
