#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
using ld=long double;
ld pie=3.141592653589793;
ll inf=10010010010010010;
ll mod=998244353;
int main(){
    ll n,k;
    cin >> n >> k;
    vector<ll>a(n);
    for (ll i = 0; i < n; i++)
    {
        cin >> a[i];
    }
    sort(a.begin(),a.end());
    vector<pair<ll,ll>>p;
    for (ll i = 0; i < n-1; i++)
    {
        p.push_back({a[i+1]-a[i],i});
    }
    sort(p.begin(),p.end());
    reverse(p.begin(),p.end());
    vector<ll>memo(n+100,0);
    for (ll i = 0; i < k-1; i++)
    {
        memo[p[i].second]=1;
    }
    ll ans=0;
    ll now=a[0];
    for (ll i = 0; i < n; i++)
    {
        if (memo[i]>=1)
        {
            ans+=a[i]-now;
            now=a[i+1];
        }else{
            if (i==n-1)
            {
                ans+=a[i]-now;
            }
        }
    }
    cout << ans << endl;
}