#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
const bool typetest = 0;
const int N = 1e5 + 5;
int n, k;
ll a[N], b[N];
void Read()
{
cin >> n >> k;
for (int i = 1; i <= n; ++i)
cin >> a[i];
for (int i = 1; i < n; ++i)
b[i] = a[i + 1] - a[i];
}
void Solve()
{
sort(b + 1, b + n);
a[n] -= a[1];
for (int i = n - 1; i >= n - k + 1; --i)
a[n] -= b[i];
cout << a[n] + k;
}
int32_t main()
{
//ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t(1);
if (typetest)
cin >> t;
for (int _ = 1; _ <= t; ++_)
{
Read();
Solve();
}
}
