#include <bits/stdc++.h>
#define control cout<<"e ne"<<endl;
#define endl '\n'
#define int long long
using namespace std;
int a[131072],sum,k;
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
}
void solve()
{
//.
int n;
cin>>n>>k;
for(int i=1;i<=n;i++)
{
cin>>a[i];
}
sum=n;
vector <int> v;
for(int i=2;i<=n;i++)v.push_back(a[i]-a[i-1]-1);
sort(v.begin(),v.end());
for(int i=0;i<n-k;i++)sum+=v[i];
cout<<sum<<endl;
}
signed main()
{
/*
#ifdef ONLINE_JUDGE
freopen("txt.in","r",stdin)
freopen("txt.out","w",stdout)
#endif
*/
speed();
//int t; cin>>t; while(t--)
solve();
return 0;
}
/*
10 5
1
2
5
6
8
11
13
15
16
20
*/
