#include<bits/stdc++.h> using namespace std; int main() { ios_base::sync_with_stdio(0); int l = 1e9,p = 0,n,k,x,po; cin >> n >> k >> l; po = l; vector<int> tab; for(int i = 1;i < n;++i) { cin >> x; p = x; tab.push_back(-(x-po-1)); po = x; //cout << x-po-1 << endl; } sort(tab.begin(),tab.end()); int wyn = p-l+1; for(int i = 1;i < k;++i) { wyn += tab[i-1]; } cout << wyn; }