#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
#include "bits/stdc++.h"
using namespace std;
#define pb push_back
#define F first
#define S second
#define f(i,a,b) for(int i = a; i < b; i++)
#define endl '\n'
using ll = long long;
using db = long double;
using ii = pair<int, int>;
const int N = 2e5 + 5, LG = 19, MOD = 1e9 + 7;
const int SQ =225;
const long double EPS = 1e-7;
string s;
int32_t main(){
#ifdef ONLINE_JUDGE
ios_base::sync_with_stdio(0);
cin.tie(0);
#endif
int n, k;
cin >> n >> k;
vector<int> v(n);
vector<int> times;
int ans = n;
for(int i = 0; i < n; i++){
cin >> v[i];
if(i)times.push_back(v[i] - v[i-1] - 1);
}
sort(times.begin(),times.end());
k = n - k;
times.resize(k);
cout << ans + accumulate(times.begin(),times.end(),0ll) << endl;
return 0;
}
