//Sorry but iam targeting IOI :))
//NEVER LOSE HOPE
#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>
#define endl "\n"
#define ceil(a,b) (a+(b-1))/b
#define all(v) v.begin(),v.end()
#define int long long int
#define Hidden ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
using namespace std;
const int N=3e4+10,mod = 1e9+7;
int32_t main(){
int n , k ;
cin >> n >> k ;
vector<int>guests(n),diff;
for(int i = 0 ; i < n ; i ++)
{
cin>>guests[i];
}
long long ans=n;
for(int i = 1 ; i < n ; i ++)
{
diff.push_back(guests[i]-guests[i-1]-1);
ans+=diff.back();
}
sort(all(diff));
//cout<<ans<<endl;
for(int i = diff.size()-1 ; i>=0 && k>1 ; i-- , k--)
{
ans-=diff[i];
}
cout<<ans;
}
