#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define watch(x) cout<<(#x)<<"="<<(x)<<'\n'
#define mset(d,val) memset(d,val,sizeof(d))
#define setp(x) cout<<fixed<<setprecision(x)
#define forn(i,a,b) for(int i=a;i<b;i++)
#define fore(i,a,b) for(int i=a;i<=b;i++)
#define pb push_back
#define F first
#define S second
#define INF 2e14
#define MOD 998244353
#define pqueue priority_queue
#define fbo find_by_order
#define ook order_of_key
typedef long long ll;
typedef pair<ll,ll> ii;
typedef vector<ll> vi;
typedef vector<ii> vii;
typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> pbds;
#define MAXN 100005
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
int n,k; cin>>n>>k;
vi gap;
ll arr[MAXN];
forn(i,0,n) cin>>arr[i];
forn(i,0,n-1){
gap.pb(arr[i+1]-arr[i]-1);
}
sort(gap.begin(),gap.end());
ll ans=0;
forn(i,0,n-k){
ans+=gap[i];
}
cout<<n+ans<<'\n';
return 0;
}
