#include "bits/stdc++.h"
using namespace std;
#define int long long
#define endl '\n'
#define all(v) v.begin(), v.end()
const long long sz = 1e5 + 5;
const long long sz1 = 1e7 + 5;
const long long inf = 1e18 + 1;
const long long mod = 1e9 + 7;
int a[sz];
void solve() {
int n, k;
cin >> n >> k;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
if (k == n) {
cout << k << endl;
return;
}
if (k == 1) {
cout << a[n] << endl;
return;
}
vector<int> dif;
for (int i = 2; i <= n; i++) {
dif.push_back(a[i] - a[i - 1]);
}
sort(all(dif));
int cnt = n - k, ans = k;
for (auto d : dif) {
if (cnt > 0) {
ans += d;
cnt--;
} else break;
}
cout << ans << endl;
}
signed main() {
cin.tie(nullptr)->sync_with_stdio(0);
int T = 1;
// cin >> T;
while (T--) {
solve();
}
return 0;
}
