#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pi pair<int,int>
#define rep(x,start,end) for(auto x=(start)-((start)>(end));x!=(end)-((start)>(end));((start)<(end)?x++:x--))
#define getunique(v) {sort(v.begin(), v.end()); v.erase(unique(v.begin(), v.end()), v.end());}
const ll INF = -1;
const int mx = 1e5+5;
const int modulo =1e9+7;
mt19937 mt;
void solve(){
int n,k;
cin>>n>>k;
vector<int> arr(n);
rep(x,0,n) cin>>arr[x];
vector<int> distances;
ll ans = n;
rep(x,1,n){
distances.push_back(arr[x]-arr[x-1]-1);
}
sort(distances.begin(),distances.end(),greater<int>());
while(n>k){
// cout<<n<<" "<<k<<'\n';
ans+=distances.back();
distances.pop_back();
n--;
}
cout<<ans<<"\n";
}
int main(){
ios_base ::sync_with_stdio(0), cin.tie(0);
clock_t start, end;
start = clock();
int t = 1;
// cin >> t;
// int x=0;
while (t-->0)
{
//cout<<"Case #"<<x<<": ";
solve();
// x++;
}
end = clock();
cerr << double(end - start) / double(CLOCKS_PER_SEC) << '\n';
}
