#include <bits/stdc++.h>
#define ll long long
#define ff first
#define ss second
#define pb push_back
#define eb emplace_back
#define inf INT_MAX
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define FAR(i, a, b) for (int i = (a); i >= (b); i--)
#define all(x) x.begin(), x.end()
const int MOD = 1e9 + 7;
using namespace std;
void solve()
{
int n, k, ans;
cin >> n >> k;
int a[n], d[n - 1];
FOR(i, 0, n)
cin >> a[i];
ans = n;
FOR(i, 0, n - 1)
d[i] = a[i + 1] - a[i] - 1;
sort(d, d + n - 1);
FOR(i, 0, n - k)
ans += d[i];
cout << ans << endl;
}
int main()
{
int T = 1;
// cin >> T;
while (T--)
{
solve();
}
return 0;
}
