#include <bits/stdc++.h>
#include <iomanip>
#define ll long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define endl "\n"
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define vi vector<int>
#define vll vector<long long>
#define F first
#define S second
#define PB push_back
#define MP make_pair
using namespace std;
const int mxn = 1e5 + 5;
const int inf = 1e9;
void solve() {
ll n, K;
cin >> n >> K;
ll sum = 0;
vll t(n), mxdiff(n + 1, 0);
for (ll i = 0; i < n; i++) {
cin >> t[i];
}
sum = t[n - 1] - t[0] + 1;
for (ll i = 1; i < n - 1; i++) {
mxdiff[i] = t[i] - t[i - 1] - 1;
}
sort(mxdiff.begin(), mxdiff.end());
reverse(mxdiff.begin(), mxdiff.end());
ll mx = 0;
for (ll i = 0; i < K - 1; i++) {
mx += mxdiff[i];
}
if (K == 1) {
cout << t[n - 1] - t[0] + 1 << endl;
} else if (K == n) {
cout << n << endl;
} else {
for (ll i = 0; i < K - 1; i++) {
if (t[n - 1] - t[n - 2] > mxdiff[i]) {
mx += (t[n - 1] - t[n - 2] - 1 - mxdiff[K - 2]); // do not delete
cout << sum - mx << endl;
return;
}
}
cout << sum - mx << endl;
}
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(NULL);
cout.tie(NULL);
ll t = 1;
// cin >> t;
while (t--) {
solve();
}
}
