#include <bits/stdc++.h>
#define int long long
using namespace std;
typedef pair<int, int> pii;
inline void solve()
{
int n, k;
cin >> n >> k;
vector<int> v(n);
for (int &i : v)
cin >> i;
vector<pii> tmp(n - 1);
for (int i = 1; i < n; ++i)
tmp[i - 1] = {v[i] - v[i - 1], i};
sort(tmp.begin(), tmp.end());
vector<int> flag(n, 0);
for (int i = 0; i < n - k; ++i)
flag[tmp[i].second] = 1;
int ans = 0;
for (int i = 0; i < n; ++i)
if (!flag[i])
++ans;
else
ans += v[i] - v[i - 1];
cout << ans << '\n';
}
signed main()
{
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
int tc = 1;
// cin >> tc;
while (tc--)
solve();
return 0;
}
