#include <bits/stdc++.h>
using namespace std;
#define int long long
const int INF = 1e18;
const int MOD = 26101991;
const int MAXN = 1e5;
int n, m, k;
int arr[MAXN+5];
void mulaidarinol(){}
void solve(){
cin >> n >> m;
for(int i = 1; i <= n; i++) cin >> arr[i];
sort(arr, arr+n+1);
priority_queue<int> pq;
for(int i = 1; i < n; i++){
pq.push(arr[i+1] - (arr[i] + 1));
}
m--;
int ans = arr[n] + 1 - arr[1];
while(m--){
ans -= pq.top();
pq.pop();
}
cout << ans << endl;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int tc = 1;
// cin >> tc;
while(tc--){
// mulaidarinol();
solve();
// cerr << endl;
}
return 0;
}
