#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll
using P = pair<int, int>;
#define all(x) x.begin(), x.end()
#define rep(i, l, n) for (int i = l; i < (n); ++i)
#define sz(x) (int)x.size()
const char nl = '\n';
void solve() {
int n, k; cin >> n >> k;
vector<int> t(n);
for (auto &i: t)cin >> i;
priority_queue<int, vector<int>, greater<int>> pq;
rep(i, 1, n)pq.push(t[i]-t[i-1]-1);
int res = n, s = n;
while (s > k) {
res += pq.top(); pq.pop();
s--;
}
cout << res << nl;
}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
