#include <algorithm>
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#define line() "author : AyazN";
#endif
#define all(x) (x).begin(), (x).end()
#define isz(x) (int)(x.size())
#define int ll
typedef long double ld;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pii> vpii;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
const int sz = 500000, inf = 1000000000, LOG = 20;
const ll mod = 1000000007, INF = 1000000000000000000;
int a[sz];
void run_case(int tc) {
int n, k;
cin >> n >> k;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
int sm = n;
multiset<int> st;
for (int i = 2; i <= n; i++) st.insert(a[i] - a[i - 1] - 1);
k = n - k;
while (k--) {
sm += *(st.begin());
st.erase(st.begin());
}
cout << sm << '\n';
}
void precompute() {}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
#ifdef LOCAL
// freopen("err.log", "w", stderr);
#endif
precompute();
int t = 1; // cin >> t;
for (int tc = 1; tc <= t; tc++) {
run_case(tc);
}
}
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