#include <iostream>
#include <vector>
#include <cstring>
#include <string>
#include <iomanip>
#include <algorithm>
#include <fstream>
#include <cmath>
#include <unordered_set>
#include <set>
#include <unordered_map>
#include <queue>
#define ll long long
#define X first
#define Y second
#define endl '\n'
using namespace std;
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
}
int n,k;
const int MAXN=100100;
int t[MAXN];
void read()
{
cin>>n>>k;
for(int i=1;i<=n;i++)
{
cin>>t[i];
}
t[n+1]=1e9+5;
}
vector<pair<int,int>> inter;
void sweep()
{
int beg=t[1];
for(int i=2;i<=n+1;i++)
{
if(t[i]==t[i-1]+1)continue;
inter.push_back({t[i-1]-beg+1,1});
inter.push_back({t[i]-t[i-1]-1,0});
beg=t[i];
}
inter.pop_back();
}
signed main()
{
speed();
read();
sweep();
int ans=n;
int cnt=0;
priority_queue<int> q;
for(pair<int,int> e:inter)
{
//cout<<e.X<<' '<<e.Y<<endl;
if(e.Y==0)
{
q.push(-e.X);
}
else
{
cnt++;
}
}
while(cnt>k)
{
ans+=-q.top();
cnt--;
q.pop();
}
cout<<ans<<endl;
return 0;
}
