#include <bits/stdc++.h>
#include <experimental/random>
#include <random>
//#include <ext/pb_ds/assoc_container.hpp>
//using namespace __gnu_pbds;
using namespace std;
using ld = long double;
using ll = long long;
const ll INF = 3e18, MOD = 1e9 + 7;
void solve();
signed main() {
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
ios::sync_with_stdio(false);
cin.tie(0);
int q = 1;
//cin >> q;
while (q--) {
solve();
}
}
void solve() {
ll n, k;
cin >> n >> k;
vector<ll> t(n);
for (int i = 0; i < n; i++) {
cin >> t[i];
}
vector<ll> z;
ll len = t.back() + 1 - t[0];
for (int i = 1; i < n; i++) {
z.push_back(t[i] - t[i - 1] - 1);
}
sort(z.rbegin(), z.rend());
for (int i = 0; i < min(k - 1, (ll)z.size()); i++) {
len -= z[i];
}
cout << len;
}
