#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#define fst first
#define snd second
#define pb push_back
#define forn(i,a,b) for(int i = a; i<b; i++)
#define SZ(x) (int)x.size()
#define ALL(x) x.begin(),x.end()
#define mset(a,v) memset(a,v,sizeof(a))
#define FIN ios::sync_with_stdio(0); cout.tie(); cin.tie(0);
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update> iset;
int main(){
ll n,k; cin>>n>>k;
vector<ll> t(n); forn(i,0,n) cin>>t[i];
ll res = n;
vector<ll> opt;
forn(i,0,n-1){
opt.pb(t[i+1]-t[i]);
}
sort(ALL(opt));
forn(i,0,n-k){
res+=opt[i]-1;
}
cout<<res<<'\n';
return 0;
}
