#include<bits/stdc++.h>
using namespace std;
#define i64 long long
#define mp make_pair
#define pb push_back
#define all(x) (x).begin(), (x).end()
void Solve(void) {
int N, K; cin >> N >> K;
vector<int> T(N + 1);
vector<bool> en(N + 1, false);
vector<pair<int, int>> d;
for (int i = 1; i <= N; i ++) {
cin >> T[i];
if (i > 1) {
d.pb(mp(T[i] - T[i - 1], i - 1));
}
}
sort(d.rbegin(), d.rend());
for (int i = 0; i < K - 1; i ++) {
en[d[i].second] = true;
// cout << d[i].second << "\n";
}
int prev = -1;
i64 ans = 0;
for (int i = 1; i <= N; i ++) {
if (prev == -1) prev = T[i];
if (en[i]) {
ans += T[i] + 1 - prev;
prev = -1;
}
}
if (prev != -1) ans += T[N] + 1 - prev;
cout << ans << "\n";
}
signed main() {
ios_base::sync_with_stdio(false); cin.tie(0);
int Tests = 1; // cin >> Tests;
while (Tests --) {
Solve();
}
}
