#include "bits/stdc++.h"
using namespace std;
#define fi first
#define se second
#define ll long long
#define dbg(v) cerr<<#v<<" = "<<v<<'\n'
#define vi vector<int>
#define vl vector <ll>
#define pii pair<int,int>
#define mp make_pair
#define db long double
#define pb push_back
#define all(s) s.begin(),s.end()
template < class T > T smin(T &a,T b) {if (a > b) a = b;return a;}
template < class T > T smax(T &a,T b) {if (a < b) a = b;return a;}
int main(void) {
int n,k;
cin>>n>>k;
vi s(n);
for (auto & it : s)
cin>>it;
int ans = s.back() - s[0] + 1;
vi v;
--k;
for (int i = 1;i < n;++i)
v.pb(s[i] - s[i - 1] - 1);
sort(all(v),greater < int > ());
for (int i = 0;i < k;++i)
ans -= v[i];
cout << ans << '\n';
return 0;
}
