#include<bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define sz() size()
#define all(v) (v).begin(),(v).end()
#define F first
#define S second
#define pb push_back
#define popb pop_back
#define ss sort
#define rr reverse
#define pii pair <int, int>
#define pll pair <ll, ll>
using namespace std;
using ld = long double;
using ll = long long;
const int N = 2e5+10;
const ll inf = 1e18;
const int Mod = 1e9+7;
const int P = 273;
int n, k, a[N];
void Erali_is_the_best(int testCase)
{
cin >> n >> k;
vector <int> vec;
for (int i = 1; i <= n; ++i)
{
cin >> a[i];
if (i > 1) vec.pb(a[i] - a[i-1] - 1);
}
int ans = n;
ss(all(vec));
for (int i = 0; i < n - k; ++i)
{
ans += vec[i];
}
cout << ans << "\n";
}
int32_t main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
// freopen("cardgame.in","r",stdin);
// freopen("cardgame.out","w",stdout);
int tt = 1;
// cin >> tt;
for (int test = 1; test <= tt; ++test)
{
Erali_is_the_best(test);
}
}
