//Suleyman Atayew
#include <algorithm>
#include <iostream>
#include <string.h>
#include <stdio.h>
#include <vector>
#include <bitset>
#include <queue>
#include <cmath>
#include <map>
#include <set>
#define N 200010
#define ff first
#define ss second
#define pb push_back
#define ll long long
#define mod 1000000007
#define pii pair <int, int>
#define sz(a) (int)(a.size())
ll bigmod(ll a, ll b) { if(b==0)return 1; ll ret = bigmod(a, b/2); return ret * ret % mod * (b%2 ? a : 1) % mod; }
using namespace std;
int n, k;
int v[N];
vector <pii> V;
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n >> k;
for(int i = 1; i <= n; i++)
cin >> v[i];
int ans = 0;
for(int i = 1; i <= n; i++) {
int x = i;
while(v[i] == v[i+1]-1) i++;
V.pb({v[x], v[i]});
ans += v[i]-v[x]+1;
}
vector <int> dis;
for(int i = 1; i < sz(V); i++)
dis.pb(V[i].ff-V[i-1].ss-1);
sort(dis.begin(), dis.end());
for(int i = 0; i < sz(V)-k; i++)
ans += dis[i];
cout << ans;
}
