#include<bits/stdc++.h>
#include<algorithm>
#include<random>
#include<chrono>
#include<cstdlib>
#include<ctime>
#include<numeric>
#include<vector>
#include<stack>
#include<map>
#include<set>
#include<queue>
#include<iomanip>
#define int long long
#define ll long long
#define L LLONG_MAX
#define fi first
#define se second
#define pii pair<int,int>
#define sz(a) ((int)a.size())
#define FOR(i,j,k) for(int i=j;i<=k;i++)
#define REP(i,k,j) for(int i=k;i>=j;i--)
#define FORD(i,a) for(auto i:a)
#define rngdcl mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count())
#define random(l,r) ((l)+(rng()%(r-l+1)))
using namespace std;
const int nmax=1e5+1;
int n,k;
int a[nmax];
void input()
{
cin >> n >> k;
FOR(i,1,n) cin >> a[i];
}
void solve()
{
vector<int> save;
int ans=a[n]-a[1]+1;
FOR(i,1,n-1) save.push_back(a[i+1]-a[i]);
sort(save.begin(),save.end(),greater<int>());
FOR(i,0,k-2) ans-=save[i];
cout << ans+k-1;
}
signed main()
{
//freopen(".inp", "r", stdin);
//freopen(".out", "w", stdout);
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
input();
solve();
}
