#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define sz(x) (x).size()
#define all(x) (x).begin(), (x).end()
using namespace std;
string alphabet = "abcdefghijklmnopqrstuvwxyz";
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ull n,k;
cin >> n >> k;
vector <ull> a(n),pref(n - 1);
ull mx = 0,mn = 999999999999999;
for(ull i = 0; i < n; i++)
{
cin >> a[i];
mx = max(mx,a[i]);
mn = min(mn,a[i]);
if(i != 0)
{
pref[i - 1] = a[i] - a[i - 1];
}
}
ull sum = mx - mn + 1;
if(k == 1)
{
cout << (a[n - 1] - a[0]) + 1;
}
else if(n == k)
{
cout << n;
}
else
{
sort(all(pref));
reverse(all(pref));
for(ull i = 0; i < k - 1; i++)
{
sum -= pref[i] - 1;
}
cout << sum;
}
return 0;
}
/*
*/
