// ﷽ #include <bits/stdc++.h> using namespace std; #define ll long long void solve(){ ll n,k; cin>>n>>k; vector<ll> s; k--; ll first, prev; cin >> first; prev = first; for(int i=1;i<n;i++){ ll x; cin >> x; s.push_back(x - prev - 1); prev = x; } ll ans = (prev + 1) - first; sort(s.rbegin(), s.rend()); for(int i=0;i<k && i<(int)s.size();i++){ ans -= s[i]; } cout << ans << endl; } int main(){ ll n=1; while(n--){ solve(); } }