#include <bits/stdc++.h>
using namespace std;
#define sum(a) ( accumulate ((a).begin(), (a).end(), 0ll))
#define mine(a) (*min_element((a).begin(), (a).end()))
#define maxe(a) (*max_element((a).begin(), (a).end()))
#define mini(a) ( min_element((a).begin(), (a).end()) - (a).begin())
#define maxi(a) ( max_element((a).begin(), (a).end()) - (a).begin())
#define int long long
#define F first
#define S second
#define vi vector<int>
#define vvi vector<vi>
#define pb push_back
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define read(a) for(auto &x:a) cin >> x;
#define print(a) for(auto x:a) cout << x << " "; cout << "\n";
#define endl '\n'
#define sz(x) (int)size(x)
#define rsz(a,x) assign(a,x)
const int INF = LLONG_MAX;
const int MOD = 1000000007;
const int MAXN = 100005;
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n,k; cin >> n >> k;
vi a(n), dif;
for (int i=0; i<n; i++) cin >> a[i];
int ans = a[n-1]-a[0]+1;
for (int i=1; i<n; i++)
dif.pb(a[i]-a[i-1]-1);
sort(rall(dif));
for (int i=0; i<k-1; i++)
ans-=dif[i];
cout << ans << endl;
}
