#include <iostream>
#include <cstring>
#include <algorithm>
#include <vector>
#include <utility>
#include <cmath>
#include <ctime>
#include <cassert>
#include <set>
#include <stack>
#include <map>
#include <queue>
#include <random>
#include <chrono>
#include <bitset>
#include <array>
using ll = long long;
#define debug(x) cout << #x << " = " << x << '\n'
#define separator "===============================================\n"
#define all(a) a.begin(), a.end()
#define SZ(a) (int)(a).size()
using namespace std;
const int mxn = 1e5 + 3;
const ll mod = 1e9 + 7;
const int inf32 = 2e9;
const ll inf64 = 3e18;
// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
void solve(){
int n, k;
cin >> n >> k;
vector<int> t(n), d(n - 1);
for (int i = 0; i < n; ++i)
cin >> t[i];
for (int i = 0; i < n - 1; ++i)
d[i] = t[i + 1] - t[i] - 1;
sort(all(d), greater<>());
int res = t[n - 1] - t[0] + 1;
for (int i = 0; i < k - 1; ++i)
res -= d[i];
cout << res << '\n';
}
int main(){
auto start = chrono::steady_clock::now();
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int t = 1;
// cin >> t;
while(t--) solve();
chrono::duration<double> elapsed {chrono::steady_clock::now() - start};
cerr << "\n>> Runtime: " << elapsed.count() << "s\n";
}
