#include "bits/stdc++.h"
#include "chrono"
using namespace std;
using namespace std::chrono;
// #pragma GCC target ("avx2")
// #pragma GCC optimization ("O3")
// #pragma GCC optimization ("unroll-loops")
// #pragma optimization_level 3
// #pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define pb push_back
#define galen_colin {ios_base::sync_with_stdio(false);}
#define orz {cin.tie(NULL); cout.tie(NULL);}
#define fix(prec) {cout << setprecision(prec) << fixed;}
#define mp make_pair
#define f first
#define s second
#define all(v) v.begin(), v.end()
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpi;
typedef vector<pll> vpl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
template<typename A> ostream& operator<<(ostream &cout, vector<A> const &v);
template<typename A, typename B> ostream& operator<<(ostream &cout, pair<A, B> const &p) { return cout << "(" << p.f << ", " << p.s << ")"; }
template<typename A> ostream& operator<<(ostream &cout, vector<A> const &v) {
cout << ""; for(int i = 0; i < v.size(); i++) {if (i) cout << " "; cout << v[i];} return cout << "\n";
}
template<typename A, typename B> istream& operator>>(istream& cin, pair<A, B> &p) {
cin >> p.first;
return cin >> p.second;
}
template<typename A> istream& operator>>(istream& cin, vector<A> &v) {
for(auto &x:v)cin>>x;
return cin;
}
ll min(ll a, int b){return min(a, (ll) b);}
ll min(int a, ll b){return min(b, (ll) a);}
ll max(ll a, int b){return max(a, (ll) b);}
ll max(int a, ll b){return max(b, (ll) a);}
void usaco(string filename) {
// #pragma message("be careful, freopen may be wrong")
freopen((filename + ".in").c_str(), "r", stdin);
freopen((filename + ".out").c_str(), "w", stdout);
}
const ld pi = 3.14159265358979323846;
// const ll mod = 1000000007;
const ll mod = 998244353;
// ll mod;
const ll INF = 1e9+7;
ll n, m, k, q, l, r, x, y, z;
const ll sz = 1e6 + 1;
string s, t;
ll ans = 0;
void solve(int tc = 0) {
cin>>n>>k;
int last = -1;
vi op;
for(int i=0;i<n;i++){
cin>>x;
if(last!=-1){
op.pb(x - last );
}
last = x+1;
}
k--;
sort(op.rbegin(), op.rend());
ll ans =0;
while(op.size() > k){
ans += op.back();
op.pop_back();
}
cout<<n + ans<<"\n";
}
int main() {
#ifdef HACKX
auto begin = std::chrono::high_resolution_clock::now();
#endif
galen_colin orz
// usaco("cowland");
int tc = 1;
//cin >> tc;
for (int t = 0; t < tc; t++) solve(t);
#ifdef HACKX
auto end = std::chrono::high_resolution_clock::now();
cout << setprecision(4) << fixed;
// cout << "Execution time: " << std::chrono::duration_cast<std::chrono::duration<double>>(end - begin).count() << " seconds" << endl;
#endif
}
