#include <bits/stdc++.h>
#define IO ios::sync_with_stdio(false);cin.tie(0);
#define debug(x) cerr << #x << " = " << (x) << ' '
#define bug(x) cerr << (x) << ' '
#define endl cerr << '\n'
#define all(v) (v).begin(), (v).end()
#define SZ(v) (ll)(v).size()
#define lowbit(x) (x)&-(x)
#define pb emplace_back
#define F first
#define S second
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
//#define TEST
const int N = 1e5+5;
int a[N];
priority_queue<int, vector<int>, greater<int> > pq;
int main(void)
{ IO
int n, i, K, cur, ans = 0;
cin >> n >> K;
for (i=1; i <= n; ++i) cin >> a[i];
for (i=2; i <= n; ++i) pq.push(a[i]-a[i-1]-1);
ans = cur = n;
while (cur > K)
{
ans += pq.top(); pq.pop();
--cur;
}
cout << ans << '\n';
return 0;
}
