#include<bits/stdc++.h>
using namespace std;
ostream& operator<<(ostream &out, string str) {
for(char c : str) out << c;
return out;
}
template<class L, class R> ostream& operator<<(ostream &out, pair<L, R> p) {
return out << "(" << p.first << ", " << p.second << ")";
}
template<class T> auto operator<<(ostream &out, T a) -> decltype(a.begin(), out) {
out << "{";
for(auto it = a.begin(); it != a.end(); it = next(it))
out << (it != a.begin() ? ", " : "") << *it;
return out << "}";
}
void dump() { cerr << "\n"; }
template<class T, class... Ts> void dump(T a, Ts... x) {
cerr << a << ", ";
dump(x...);
}
#ifdef DEBUG
# define debug(...) cerr << "[" #__VA_ARGS__ "]: ", dump(__VA_ARGS__)
#else
# define debug(...) false
#endif
#define REP(i, n) for(int i = 0; i < n; i++)
#define FOR(i, a, b) for(int i = a; i <= b; i++)
#define ST first
#define ND second
template<class T> int size(T && a) { return a.size(); }
using LL = long long;
using PII = pair<int, int>;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, k;
cin >> n >> k;
vector<int> t(n);
REP(i, n) cin >> t[i];
int ans = t[n - 1] + 1 - t[0];
vector<int> delta(n - 1);
REP(i, n - 1)
delta[i] = t[i + 1] - t[i] - 1;
sort(delta.rbegin(), delta.rend());
REP(i, min(n - 1, k - 1))
ans -= delta[i];
cout << ans << "\n";
}
