//hafo
#include <bits/stdc++.h>
#define ll long long
#define ull unsigned ll
#define pb push_back
#define pa pair<int, int>
#define pall pair<ll, int>
#define fi first
#define se second
#define TASK "test"
#define Size(x) (int) x.size()
#define all(x) x.begin(), x.end()
using namespace std;
template<typename T1, typename T2> bool mini (T1 &a, T2 b) {if(a > b) a = b; else return 0; return 1;}
template<typename T1, typename T2> bool maxi (T1 &a, T2 b) {if(a < b) a = b; else return 0; return 1;}
const int MOD = 1e9 + 7;
const int LOG = 20;
const int maxn = 2e5 + 7;
const ll oo = 1e18 + 69;
int n, k, a[maxn];
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
//freopen(TASK".inp", "r", stdin);
//freopen(TASK".out", "w", stdout);
cin>>n>>k;
for(int i = 1; i <= n; i++) cin>>a[i];
sort(a + 1, a + 1 + n);
int ans = a[n] + 1 - a[1];
vector<int> val;
for(int i = 2; i <= n; i++) val.pb(a[i] - a[i - 1] - 1);
sort(all(val), greater<int>());
for(int i = 0; i < k - 1; i++) ans -= val[i];
cout<<ans;
return 0;
}
