#include<bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
typedef long long ll;
typedef pair<ll,ll> pll;
typedef pair<ll,int> pli;
typedef pair<int,ll> pil;
typedef pair<int,int> pii;
const ll INFLL=1e18+7;
const int INF=1e9+7;
#define pb push_back
const int MAXN=1e5+7;
int arr[MAXN];
int main()
{
ios_base::sync_with_stdio(0);
int n,k; cin>>n>>k;
for(int i=1;i<=n;++i) cin>>arr[i];
int total=arr[n]-arr[1]+1;
vector<int> segments;
for(int i=1;i<n;++i){
segments.pb(arr[i+1]-arr[i]-1);
}
sort(segments.begin(),segments.end());
reverse(segments.begin(),segments.end());
for(int i=0;i<k-1;++i) total-=segments[i];
cout<<total<<"\n";
}
