#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll, ll>
#define pii pair<int, int>
#define fs first
#define sc second
#define pb push_back
void solve() {
int n,k;
cin>>n>>k;
int a[n];
for(int i=0;i<n;i++)cin>>a[i];
int d[n-1],c=n;
for(int i=0;i<n-1;i++)d[i]=a[i+1]-a[i]-1;
sort(d,d+n-1);
for(int i=0;i<n-k;i++)c+=d[i];
cout<<c<<'\n';
}
int main() {
#ifdef FPO
freopen("in","r",stdin);
freopen("out","w",stdout);
#endif
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
solve();
}
