#include <bits/stdc++.h>
#define endl '\n'
#define ll long long
using namespace std;
const int N = 1e5+5;
int n,k;
ll ar[N+3];
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin>>n>>k;
--k;
vector<int>vec;
ll sum=0;
for(int i=1;i<=n;i++)cin>>ar[i];
for(int i=1;i<n;i++){
vec.emplace_back(ar[i+1]-ar[i]-1);
sum+=ar[i+1]-ar[i]-1;
//cout<<ar[i+1]-ar[i]-1<<endl;
}
// cout<<sum;
// cout<<endl;
sort(vec.rbegin(),vec.rend());
for(int i=0;i<=min(k-1,int(vec.size())-1);i++){
sum-=vec[i];
//cout<<vec[i]<<endl;
}
cout<<n+sum;
return 0;
}
/*
10 5
1
2
5
6
8
11
13
15
16
20
*/
