#include <bits/stdc++.h>
using namespace std;
#define int long long
#define form2(i, a, b) for (int i = (a); i < (b); ++i)
#define ford2(i, a, b) for (int i = (a-1); i >= b; --i)
#define form(i, n) form2(i, 0, n)
#define ford(i, n) ford2(i, n, 0)
#define chmax(x, v) x = max(x, (v))
#define chmin(x, v) x = min(x, (v))
#define fi first
#define se second
#define BIG 1000000000000000000
typedef long long ll;
typedef long double ld;
void cpr(string s, vector<int> v)
{ int i = 0; for (char c : s) { if (c == '$') cout << v[i++]; else cout << c; } cout << '\n'; }
void cpr(string s) { cpr(s, {}); }
void solve();
signed main()
{
ios::sync_with_stdio(false);
cin.tie(0);
solve();
return 0;
}
void solve()
{
int n, k;
cin >> n >> k;
vector<int> a(n);
vector<int> d(n-1);
form(i, n) {
cin >> a[i];
if (i) d[i-1] = a[i] - a[i-1];
}
sort(d.begin(), d.end());
int tot = a.back() + 1 - a.front();
form(i, k-1) {
tot -= d.back()-1;
d.pop_back();
}
cout << tot << "\n";
}
