#include<bits/stdc++.h> using namespace std; #define int long long signed main() { int n,k ; cin >> n >> k; vector<int> t(n); for (int i=0 ;i<n;i ++) cin>>t[i]; sort(t.begin(),t.end()); vector<int> diff; for (int i=1;i<n;i++) { diff.push_back((t[i]-t[i-1])-1); }sort(diff.rbegin(),diff.rend()); int ans=t[n-1]-t[0]+1; for (int i=0;i<k-1&& i < diff.size();i++)ans-=diff[i]; cout<<ans<<endl; return 0; }