#include <bits/stdc++.h>
using namespace std;
#define ull unsigned long long
#define int long long
#define prq priority_queue
#define pb push_back
#define pf push_front
#define pr pair<int,int>
#define ff first
#define ss second
#define sorta sort(a,a+n)
#define reversea reverse(a,a+n)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define hurryup ios::sync_with_stdio(0); cin.tie(nullptr); cout.tie(nullptr);
const int INF=1e18;
const int MOD=1e9 + 7;
signed main() {
hurryup;
int n,k;
cin>>n>>k;
int a[n];
for(int i=0; i<n; i++) cin>>a[i];
int res=a[n-1]-a[0]+1;
vector<int> v;
for(int i=0; i<n-1; i++) {
v.pb(a[i+1]-a[i]-1);
}
sort(rall(v));
for(int i=0; i<k-1; i++) {
res-=v[i];
}
cout<<res;
}
// by Maharram Gurbanzada
