#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define endl '\n'
#define INF 1e9+7
#define all(x) x.begin(),x.end()
using namespace std;
using namespace __gnu_pbds;
using ll=long long;
using pii=pair<int,int>;
using ppi=pair<int,pii>;
using oset=tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>;
template<typename T>
void _print(vector<T> x) {cerr<<"{"; for(auto e:x) cerr<<e<<","; cerr<<"}";}
void _print(pii x) {cerr<<"{"<<x.first<<","<<x.second<<"}";}
template<typename T>
void _print(T x) {cerr<<x;}
void dbg() {cerr<<endl;}
template<typename Head,typename... Tail>
void dbg(Head H,Tail... T) {
_print(H);
if(sizeof...(T)) cerr<<",";
else cerr<<"\"]";
dbg(T...);
}
#define debug(...) cerr<<"["<<#__VA_ARGS__<<"]:[\"",dbg(__VA_ARGS__)
const int mxn=1e5+10;
int n,k;
vector<int> diff;
int main () {
ios::sync_with_stdio(false); cin.tie(0);
cin>>n>>k;
vector<int> a(n);
for(int i=0;i<n;i++) cin>>a[i];
for(int i=1;i<n;i++) diff.push_back(a[i]-a[i-1]-1);
sort(all(diff),greater<int>());
ll ans=a[n-1]-a[0]+1;
for(int i=1;i<k;i++) ans-=diff[i-1];
cout<<ans<<endl;
}
