#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const ll N = 5e5 + 5;
const ll NN = 5e3 + 5;
const ll INF = 2e18 + 5;
const ll MOD = 1e9 + 7;
const ll P = 53;
const double eps = 1e-9;
ll a[N];
void solve() {
ll n, k;
cin >> n >> k;
for(int i = 1; i <= n; i++) {
cin >> a[i];
}
vector<ll> v;
for(int i = 2; i <= n; i++) {
if(a[i] - a[i - 1] != 1) {
v.push_back(a[i] - a[i - 1] - 1);
}
}
sort(v.rbegin(), v.rend());
ll ans = n;
for(int i = k - 1; i < v.size(); i++) {
ans += v[i];
}
cout << ans << '\n';
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
int test = 1;
// cin >> test;
for(int i = 1; i <= test; i++) {
solve();
}
return 0;
}
