#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define int long long
#define endl '\n'
using namespace std;
using namespace __gnu_pbds;
using ordered_set = tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>;
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
int n,k;
cin>>n>>k;
int arr[n];
for(auto &i:arr)cin>>i;
int ans=arr[n-1]-arr[0]+1;
priority_queue<int>pq;
for(int i=1;i<n;i++)pq.push(arr[i]-arr[i-1]-1);
int f=1;
while(++f<=k&&pq.size()){
ans-=pq.top();
pq.pop();
}
cout<<ans;
}
