//#pragma GCC target("tune=native")
//#pragma GCC optimize("03,inline,Ofast,unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define int long long
vector<vector<int>>adj;
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n,k;
cin>>n>>k;
vector<int>a(n);
int toplam=0;
for(int i=0;i<n;i++)cin>>a[i];
toplam=a[n-1]+1-a[0];
vector<int>ara;
for(int i=1;i<n;i++) {
ara.push_back(a[i]-a[i-1]-1);
//cout<<ara[i]<<" ";
//cout<<a[i]-a[i-1]-1<<endl;
}
k--;
int l=ara.size();
//cout<<l<<endl;
int i=0;
sort(ara.begin(),ara.end());
reverse(ara.begin(),ara.end());
while(k>0&&i<l) {
toplam -= ara[i];
i++;
k--;
}
cout<<toplam<<endl;
return 0;
}
