#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define fbo find_by_order
#define ook order_of_key
typedef long long ll;
typedef pair<int,int> ii;
typedef vector<int> vi;
typedef long double ld;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
typedef set<int>::iterator sit;
typedef map<int,int>::iterator mit;
typedef vector<int>::iterator vit;
ll a[111111];
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
int n,k; cin>>n>>k;
vector<ll> d;
for(int i=0;i<n;i++)
{
cin>>a[i];
if(i>0) d.pb(a[i]-a[i-1]);
}
ll ans = a[n-1]-a[0]+k;
sort(d.rbegin(),d.rend());
for(int i=0;i<k-1;i++)
{
ans-=d[i];
}
cout<<ans<<'\n';
}
