#include<bits/stdc++.h>
#define ll long long int
#define FOR(i,N) for(i=0;i<N;i++)
#define FORe(i,N) for(i=1;i<=N;i++)
#define FORr(i,a,b) for(i=a;i<b;i++)
#define ff first
#define ss second
#define mp make_pair
#define pb push_back
#define vi vector<ll>
#define ii pair<ll,ll>
#define vii vector<ii>
const ll MAXN = 1e5;
const ll LOGN = 17;
const ll ROOTN = 320;
const ll INF = 1e17+21;
const ll MOD = 1e9 + 7;
using namespace std;
int main()
{
ll N,i,K,ans = 1,prev = 0,curr = 0;
vi diff;
cin>>N>>K;
K = N-K;
cin>>prev;
ans = N;
FOR(i,N - 1)
{
cin>>curr;
diff.pb(curr - prev - 1);
prev = curr;
}
sort(diff.begin(),diff.end());
FOR(i,K)
ans += diff[i];
cout<<ans;
return 0;
}
