#include <iostream>
#include <iomanip>
#include <cassert>
#include <vector>
#include <numeric>
#include <string>
#include <bitset>
#include <cmath>
#include <algorithm>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <random>
#include <ctime>
#include <chrono>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) (int)((x).size())
typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
//typedef __int128_t int128;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const char en = '\n';
const int INF = 1e9 + 7;
const ll INFLL = 1e18;
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
void solve() {
int n, k;
cin >> n >> k;
vector<int> a(n), b(n - 1);
for (int i = 0; i < n; ++i) {
cin >> a[i];
if (i) {
b[i - 1] = a[i] - a[i - 1] - 1;
}
}
ll ans = a[n - 1] - a[0] + 1;
sort(rall(b));
for (int i = 0; i < k - 1; ++i) {
ans -= b[i];
}
cout << ans << en;
}
int main() {
#ifdef __APPLE__
freopen("input.txt", "r", stdin);
#else
ios_base::sync_with_stdio(0);
cin.tie(0);
#endif
solve();
return 0;
}
