#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize ("O2")
#pragma GCC optimize ("unroll-loops")
#define ll long long
#define pii pair<ll,ll>
#define fi first
#define sec second
#define ld long double
template <typename T>
ostream& operator << (ostream& os, vector<T>tmp){
os << "[";
for(auto x : tmp) os << " " << x;
os << " ]";
return os;
}
template <typename T>
ostream& operator << (ostream& os, set<T>tmp){
os << "[";
for(auto x : tmp) os << " " << x;
os << " ]";
return os;
}
template <typename T>
ostream& operator << (ostream& os, multiset<T>tmp){
os << "[";
for(auto x : tmp) os << " " << x;
os << " ]";
return os;
}
ostream& operator << (ostream& os, pii x){
os << "[";
os << " " << x.fi << " " << x.sec;
os << " ]";
return os;
}
const ll MOD = 998244353;
const ll N = 2e5 + 5;
const ll INF = 2e18;
// modulo operations
void add(ll &a, ll b) { a = (a + b) % MOD; }
void sub(ll &a, ll b) { a -= b; while(a < 0) a += MOD; a %= MOD; }
void mul(ll &a, ll b) { a = (a * b) % MOD; }
ll expo(ll a, ll b) {
ll ans = 1;
while(b > 0){
if(b & 1) mul(ans, a);
mul(a, a);
b /= 2;
}
return ans;
}
int32_t main(){
cin.tie(0)->sync_with_stdio(0);
int tc = 1;
// cin >> tc;
for(;tc--;){
ll n, k; cin >> n >> k;
vector<ll>t(n + 5);
vector<ll> tmp;
for(int i = 1; i <= n; i++){
cin >> t[i];
if(i > 1) tmp.push_back(t[i] - t[i - 1] - 1);
}
sort(tmp.begin(), tmp.end());
ll time = n;
for(int j = 0; j < n - k; j++){
time += tmp[j];
}
cout << time << "\n";
}
}
/*
*/
