#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
#define FAST ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);cerr.tie(0)
#define mp make_pair
#define xx first
#define yy second
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define all(x) (x).begin(),(x).end()
#define erase_uni(x) x.erase(unique(all(x)),x.end())
#define inv(n) power((n), mod - 2)
#define ff(i,a,b) for (int (i) = (a); (i) < (b); (i)++)
#define fff(i,a,b) for (int (i) = (a); (i) <= b; (i)++)
#define bff(i,a,b) for (int (i) = (b)-1; (i) >= (a); (i)--)
#define bfff(i,a,b) for (int (i) = (b); (i) >= (a); (i)--)
#define sum_overflow(a,b) __builtin_add_overflow_p ((a), (b), (__typeof__ ((a) + (b))) 0)
#define mul_overflow(a,b) __builtin_mul_overflow_p ((a), (b), (__typeof__ ((a) + (b))) 0)
using namespace std;
long double typedef ld;
unsigned int typedef ui;
long long int typedef li;
pair<int,int> typedef pii;
pair<li,li> typedef pli;
pair<ld,ld> typedef pld;
vector<vector<int>> typedef graph;
unsigned long long int typedef ull;
//const int mod = 998244353;
const int mod = 1000000007;
/*using namespace __gnu_pbds;
template <class T> using oset = tree<T, null_type,less<T>, rb_tree_tag,tree_order_statistics_node_update>;
template <class T> using omset = tree<T, null_type,less_equal<T>, rb_tree_tag,tree_order_statistics_node_update>;*/
//Note to self: Check for overflow
int a[100005];
int main()
{
FAST;
int n,k; cin>>n>>k;
ff(i,0,n) cin>>a[i];
vector<int> b;
ff(i,1,n) b.pb(a[i]-a[i-1]-1);
sort(all(b),greater<int>());
li ans=n;
for (int i=n;i>k;i--)
{
ans+=b.back();
b.popb();
}
cout<<ans<<"\n";
}
//Note to self: Check for overflow
