/*input
3 2
1
3
6
*/
#include<bits/stdc++.h>
using namespace std;
const int N=1e5 + 100;
const int mod=1e9 + 7;
#define int long long
const int inf=1e18;
#define pii pair<int, int>
#define f first
#define s second
#define mp make_pair
#define FOR(i, n) for(int i=1;i<=n;i++)
#define TRACE(x) cerr << #x << " = " << x << endl
//Trace prints the name of the variable and the value.
int ans, arr[N];vector<int> vals;
signed main()
{
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
int n, k;cin>>n>>k;
for(int i=1;i<=n;i++)
{
cin>>arr[i];
if(i>1) vals.push_back(arr[i]-arr[i-1]);
}
sort(vals.begin(), vals.end());
ans=n;
for(int i=0;i<n-k;i++)
{
ans+=vals[i]-1;
}
cout<<ans;
}
