#include <bits/stdc++.h>
#define en '\n'
#define sp ' '
#define ll long long
#define pii pair<int, int>
#define piii pair<int, pair<int, int>>
#define maxx(a,b) a=max(a,b)
#define minn(a,b) a=min(a,b)
#define st first
#define nd second
using namespace std;
int main(){ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n,k,x; cin>>n>>k;
pii a[n];
for(int i=0;i<n;i++){cin>>x; a[i]={x,x+1};}
priority_queue<int> pq;
for(int i=0;i<n-1;i++) pq.push(a[i+1].st-a[i].nd);
int i=1,ans=n;
while(!pq.empty()){
if(i>=k) ans+=pq.top();
pq.pop();
i++;
}
cout<<ans;
return 0;
}
