#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
typedef long long ll;
typedef long double ld;
using namespace __gnu_pbds;
using namespace std;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
ll n, k;
cin >> n >> k;
vector<ll> T(n+1, -1);
for(ll i=1; i<=n; ++i) cin >> T[i];
vector<ll> diff;
ll ans = T[n]-T[1]+1;
for(int i=0; i<n; ++i) diff.push_back(T[i+1]-T[i]-1);
sort(diff.begin(), diff.end());
for(int i=0; i<k-1; ++i) {
ans -= diff.back();
diff.pop_back();
}
cout << ans << "\n";
return 0;
}
