#include <bits/stdc++.h>
#define fast cin.tie(0);cout.tie(0);ios_base::sync_with_stdio(false)
#define pb push_back
#define ppb pop_back
#define fi first
#define se second
#define sp " "
// #define endl "\n"
#define mod 1000000007
#define MAXN 200005
#define MAXM 1000006
#define inf 1e18
#define INF 0x3f
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define debug(x) for(auto& a: x) cout << a << " "
using namespace std;
typedef long long int lo;
lo n,m,p,q,k,l,a,b;
lo arr[MAXN];
lo len[MAXN];
lo cnt[MAXN];
vector<lo> v[MAXN];
string s;
vector<lo> dp;
lo color[MAXN];
lo place;
void solve(){
cin >> n >> m;
for (int i = 1; i <= n; ++i)
{
cin >> arr[i];
}
sort(arr+1,arr+n+1);
lo ans = arr[n]+1 - arr[1];
vector<lo> lens;
for (int i = 1; i < n; ++i)
{
lens.pb(arr[i+1]-(arr[i]+1));
}
sort(all(lens));
// debug(lens);
// cout << endl;
// cout << ans << endl;
for (int i = 1; i < m; i++)
{
ans -= lens[lens.size()-i];
}
cout << ans << endl;
}
int main()
{
// cout << fixed << setprecision(12);
// freopen("feast.in","r",stdin);
// freopen("feast.out","w",stdout);
// fast;
int t = 1;
// cin >> t;
while(t--)
{
solve();
}
}
