#include <bits/stdc++.h>
#include <climits>
using namespace std;
#define f first
#define s second
#define all(a) a.begin(),a.end()
#define sz(a) (int)a.size()
#define int long long
const int N=1e5+5;
int n,k;
int M[N];
void solve(){
cin>>n>>k;
for(int i=1;i<=n;++i) cin>>M[i];
vector<int>can;
for(int i=1;i<n;++i) can.push_back(M[i]-M[i+1]);
sort(all(can));
int sum=M[n]-M[1]+k;
for(int i=0;i<k-1;++i) sum+=can[i];
cout<<sum;
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int T=1;
while(T--) solve();
}
