#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
const ll MAKS=1e5+5;
const ll INF=1e18;
vector<pair<ll,ll>>g[MAKS];
int main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
ll n, m;
cin>>n>>m;
vector<ll>v(n+1);
vector<ll>dif(n+1);
vector<pair<ll,ll>>ind;
for(ll i=1; i<=n; i++){
cin>>v[i];
if(i>1){
dif[i-1]=v[i]-v[i-1];
ind.pb({dif[i-1], i});
}
}
sort(ind.begin(), ind.end());
ll last=n, cem=0;
for(ll i=ind.size()-1; i>ind.size()-m; i--){
//cout<<ind[i].first<<' '<<ind[i].second<<endl;
cem+=v[last]-v[ind[i].second]+1;
last=ind[i].second-1;
}
if(last!=1){
cem+=v[last]-v[1]+1;
}
cout<<cem;
}
