#include <bits/stdc++.h>
using namespace std;
#define int long long
#define OYY LLONG_MAX
#define faster ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define fi first
#define se second
#define FOR for(int i=1;i<=n;i++)
#define mid (start+end)/2
#define pb push_back
#define lim 100005
const int mod=998244353;
int n,k;
int dizi[lim];
int32_t main(){
faster
cin>>n>>k;
FOR{
cin>>dizi[i];
}
sort(dizi+1,dizi+1+n);
int cev=dizi[n]-dizi[1]+1;
priority_queue<int> pq;
FOR{
if(i==1)continue;
pq.push(dizi[i]-dizi[i-1]-1);
}
k--;
while(k--){
cev-=pq.top();
//cout<<cev<<" "<<pq.top()<<endl;
pq.pop();
}
cout<<cev<<'\n';
return 0;
}
