#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define all(x) x.begin(), x.end()
#define nl '\n'
#define deb(x) cout << #x << ": " << x << nl;
ll ps[1<<18];
ll arr[1<<18];
void solve()
{
ll n, k; cin >> n >> k;
for (ll i = 1; i <= n; i++)
{
cin >> arr[i];
}
sort(arr+1, 1+arr+n);
for (ll i = 1; i <= n; i++)
ps[i] = -arr[i] + arr[i-1];
sort (ps+1, ps+1+n);
ll suma = arr[n]+1 - arr[1];
//deb(suma);
for (ll i = 1; i < k; i++)
{
//deb(ps[i]-1);
suma += ps[i]+1;
}
cout << suma << nl;
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
ll t = 1; //cin >> t;
while (t--)
solve();
return 0;
}
