#ifdef ONLINE_JUDGE
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#endif
#include <bits/stdc++.h>
#define ll long long int
#define speed ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define TxtIO freopen("lol.in","r",stdin); freopen("lol.txt","w",stdout);
#define forn(i,n) for(int i=0;i<n;i++)
#define pb push_back
using namespace std;
void solve(){
ll n,k;
cin>>n>>k;k--;
vector <pair<ll,ll>> v(n);
forn(i,n){
cin>>v[i].first;
v[i].second=v[i].first+1;
}
vector <ll> razn;
for(int i=0;i<n-1;i++){
razn.pb(abs(v[i].second-v[i+1].first));
}
sort(razn.begin(),razn.end());
ll ans=0;
for(int i=0;i<(n-k-1);i++){
ans+=razn[i];
}
ans+=n;
cout<<ans;
}
signed main(){
speed;
int t=1;
while(t--){
solve();
}
}
