#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define oo 1000000000000
const ll mx=1e5+5;
int main(){
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
ll n,k,cnt=1,dif=oo; cin >> n >> k;
vector<ll> t(n);
vector<pair<ll,ll>> v;
for(ll i=0;i<n;++i) {
cin >> t[i];
}
for(ll i=1;i<n;++i) {
if(t[i]==t[i-1]+1) {
++cnt;
} else {
v.push_back({dif,cnt});
cnt=1;
dif=t[i]-t[i-1]-1;
}
}
v.push_back({dif,cnt});
sort(v.rbegin(),v.rend());
ll ans=0;
for(ll i=0;i<min(k,ll(v.size()));++i) {
ans += v[i].second;
}
for(ll i=k;i<ll(v.size());++i) {
ans=ans+v[i].first+v[i].second;
}
cout << ans;
return 0;
}
