#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ld long double
#define show(x,y) cout << y << " " << #x << endl;
#define show2(x,y,i,j) cout << y << " " << #x << " " << j << " " << #i << endl;
#define show3(x,y,i,j,p,q) cout << y << " " << #x << " " << j << " " << #i << " " << q << " " << #p << endl;
#define show4(x,y) for(auto it:y) cout << it << " "; cout << #x << endl;
typedef pair<int,int>pii;
typedef pair<pii,pii>pi2;
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
void solve(){
int n,k;
cin >> n >> k;
int arr[n];
for(int x=0;x<n;x++){
cin >> arr[x];
}
sort(arr,arr+n);
vector<int>v;
for(int x=1;x<n;x++){
v.push_back(max(0LL,arr[x]-1-arr[x-1]));
}
sort(v.begin(),v.end());
reverse(v.begin(),v.end());
int counter=0;
for(int x=0;x<k-1;x++) counter+=v[x];
cout << arr[n-1]+1-arr[0]-counter;
}
int32_t main(){
ios::sync_with_stdio(0);
cin.tie(0);
//freopen("in.txt","r",stdin);
//freopen("in.txt","w",stdout);
int t=1;
//cin >> t;
while(t--){
solve();
}
}
