#include<bits/stdc++.h>
using namespace std;
#define mp make_pair
#define INF 10000000
#define MOD 1000000007
#define ll long long
#define F first
#define S second
typedef pair<ll, ll> ii;
typedef pair<ii, int> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef map<int, int> mii;
int main(){
int n, k;
cin>>n>>k;
int pr, c;
cin>>pr;
vi tot;
for(int i=0;i<n-1;i++){
cin>>c;
//cout<<c - pr<<endl;
tot.push_back(c - pr - 1);
pr = c;
}
sort(tot.begin(), tot.end());
int ans = n;
for(int i=0;i<(n-k);i++){
ans+=tot[i];
}
cout<<ans<<endl;
}
