#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pb push_back
#define ff first
#define ss second
#define MOD 1000000009
#define INF 1000000019
#define INFL 1000000000000000099LL
ll n,q,s,t,a,b,c,ans,k;
ll co[1000007],dif[1000007];
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n>>k;
for(ll i=0;i<n;i++){
cin>>co[i];
}
for(ll i=0;i+1<n;i++){
dif[i]=co[i+1]-co[i]-1;
}
sort(dif,dif+n-1);
ll res=n;
for(ll i=0;i<n-k;i++)res+=dif[i];
cout<<res;
}
