#include<bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 1e5 + 5;
int t[MAXN];
int n;
int k;
vector<int> peal;
int res = 0;
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> k;
for (int i = 1; i <= n; i++)
{
cin >> t[i];
}
res = t[n] - t[1] + 1;
if (k >= n)
{
cout << n;
return 0;
}
for (int i = 1; i < n; i++)
{
int cur = t[i + 1] - (t[i] + 1);
peal.push_back(cur);
}
sort(peal.begin(), peal.end(), greater<int>());
for (int i = 0; i < k - 1 and i < peal.size(); i++)
{
res -= peal[i];
}
cout << res;
}
