#include <bits/stdc++.h> #pragma GCC optimize("O3") #define FOR(i, x, y) for(int i = x; i < y; i++) typedef long long ll; using namespace std; ll diffs[1000001]; int main() { ios_base::sync_with_stdio(false); cin.tie(NULL); ll n, k; cin >> n >> k; ll mx, mn, curr; cin >> mn; curr = mn; FOR(i, 0, n - 1) { cin >> mx; diffs[i] = mx - curr - 1; curr = mx; } sort(diffs, diffs + n - 1, greater<ll>()); ll ans = mx - mn + 1; FOR(i, 0, k - 1) ans -= diffs[i]; cout << ans << '\n'; return 0; }