#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define ll long long
#define ii pair<ll, ll>
#define vhg ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define pp pair <long long,long long>
using namespace std;
//-------------------------------
ll a[100002], b[100002];
//-------------------------------
int main(){
vhg;
int n,k;
cin >> n >> k;
for (int i=1;i<=n;i++){
cin >> a[i];
}
for (int i=1;i<n;i++){
b[i]=a[i+1]-a[i]-1;
}
sort (b+1,b+n);
long long kq=n;
for (int i=1;i<=n-k;i++) kq=kq+b[i];
cout << kq;
}
