#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define pb push_back
#define pf push_front
#define ep emplace_back
#define ef emplace_front
#define int long long
#define ld long double
#define stoi stoll
#define all(ls) ls.begin(),ls.end()
#define allr(ls) ls.rbegin(),ls.rend()
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,tune=native")
using namespace std;
using namespace __gnu_pbds;
template<typename type>using ordered_set=tree<type,null_type,less<type>,rb_tree_tag,tree_order_statistics_node_update>;
template<typename type>using ordered_multiset=tree<type,null_type,less_equal<type>,rb_tree_tag,tree_order_statistics_node_update>;
int sum(int ls[],int n){int sum=0;for(int i=0;i<n;i++)sum+=ls[i];return sum;}
int count(string str,string word){regex regex_word(word);sregex_iterator it(all(str),regex_word);sregex_iterator end;int count=0;while(it!=end){count++;it++;}return count;}
void solve(){
int n,k;
cin>>n>>k;
int ls[n];
for(int i=0;i<n;i++)
cin>>ls[i];
int cnt=ls[n-1]-ls[0]+1;
vector<int>diff;
for(int i=1;i<n;i++){
diff.pb(ls[i]-ls[i-1]);
}
sort(all(diff),greater<int>());
for(int i=0;i<k-1;i++)
cnt-=diff[i]-1;
cout<<cnt<<endl;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(nullptr);
cout.tie(nullptr);
int t=1;
//cin>>t;
while(t--)
solve();
}
