#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#ifdef evenvalue
#include "debug.h"
#define debug(...) print(#__VA_ARGS__, __VA_ARGS__)
#else
#define debug(...)
#endif
using int64 = int64_t;
using ld = long double;
template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T>
using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T>
using min_heap = priority_queue<T, vector<T>, greater<T>>;
template<typename T>
using max_heap = priority_queue<T, vector<T>, less<T>>;
namespace read {
int Int() {
int x;
cin >> x;
return x;
}
int64 Int64() {
int64 x;
cin >> x;
return x;
}
char Char() {
char c;
cin >> c;
return c;
}
string String() {
string s;
cin >> s;
return s;
}
double Double() {
return stod(String());
}
ld LongDouble() {
return stold(String());
}
template<typename T1, typename T2>
pair<T1, T2> Pair() {
pair<T1, T2> p;
cin >> p.first >> p.second;
return p;
}
template<typename T>
vector<T> Vec(const int n) {
vector<T> v(n);
for (T &x : v) {
cin >> x;
}
return v;
}
template<typename T>
vector<vector<T>> VecVec(const int n, const int m) {
vector<vector<T>> v(n);
for (vector<T> &vec : v) {
vec = Vec<T>(m);
}
return v;
}
}//namespace read
constexpr int kInf = 1e9 + 10;
constexpr int64 kInf64 = 1e15 + 10;
constexpr int kMod = 1e9 + 7;
inline void solution() {
const int n = read::Int(), k = read::Int();
const vector<int> a = read::Vec<int>(n);
vector<int> v(n - 1);
for (int i = 0; i < n - 1; i++) {
v[i] = a[i + 1] - a[i] - 1;
}
sort(v.begin(), v.end());
reverse(v.begin(), v.end());
int ans = n;
for (int matches = n; matches > k; matches--) {
ans += v.back();
v.pop_back();
}
cout << ans << '\n';
}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
// freopen(".in", "r", stdin);
// freopen(".out", "w", stdout);
cout << fixed << setprecision(10);
int testcases = 1;
//cin >> testcases;
while (testcases--) {
solution();
}
}
