#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define f first
#define s second
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define imp cout<<-1<<"\n"
#define pb push_back
#define pii pair<int,int>
#define piii pair<int,pair<int,int>>
#define ls v<<1
#define rs v<<1|1
#define fast ios::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define ptree tree *
const int mod=1e9+7;
const int INF = 1e18;
const int N=1e5+50;
const int logn=18;
mt19937 rng(135218612);
void solve(){
int n,k;
cin>>n>>k;
k--;
vector<int>v(n+1);
set<int>s;
for(int i=1;i<=n;i++){
cin>>v[i];
if(i>1)
s.insert(v[i]-v[i-1]-1);
}
int ans=v[n]-v[1]+1;
while(k--){
auto it=s.end();
it--;
ans-=*(it);
s.erase(it);
}
cout<<ans<<"\n";
}
signed main(){
fast;
int t=1;
// cin>>t;
while(t--){
solve();
}
return 0;
}
