#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define F first
#define S second
#define pii pair<int,int>
#define vi vector<int>
#define vpii vector<pii>
#define loop(i,n) sloop(0,i,n)
#define sloop(s, i, n) for(ll i=(s);i<(n);i++)
#define rloop(i,n) rsloop(0,i,n)
#define rsloop(s,i,n) for(ll i=(n);i-->(s);)
#define all(v) (v).begin(),(v).end()
#define nie {cout<<"No\n";return;}
#define tak {cout<<"Yes\n";return;}
#ifdef DEBUG
#define DBG cout << __LINE__ << endl;
#else
#define DBG
#endif
//int xses[8] = {-1,1,0,0,-1,1,1,-1};
//int yses[8] = {0,0,-1,1,-1,1,-1,1};
#define int ll
void solve()
{
int n,k;
cin>>n>>k;
vi v(n);
loop(i,n)cin>>v[i];
vi b(n-1);
int res=n;
loop(i,n-1){
b[i]=v[i+1]-v[i]-1;
res+=b[i];
}
sort(b.rbegin(),b.rend());
//loop(i,n-1)cout<<b[i]<<' ';
//cout<<'\n';
k--;
k=min(k,n-1);
loop(i,k)res-=b[i];
cout<<res<<'\n';
}
signed main()
{
cin.tie(0);
ios_base::sync_with_stdio(0);
int t=1;
//cin>>t;
loop(i,t)
{
#ifdef DEBUG
if(t!=1)
{
cout<<"Test no. "<<i+1<<endl;
}
#endif
solve();
}
cout << '\n';
return 0;
}
