#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
// ifstream cin("milkvisits.in");
// ofstream cout("milkvisits.out");
ll i,kot,j,qqq,t,w,y,kry,mew,ttt,z,x,les,mask,l,r,k,mi,ma,q,kol,sum,m,n;
vector<ll> b,a,c;
cin>>n>>k;
for(i=0;i<n;i++)
{
cin>>x;
b.push_back(x);
}
sort(b.begin(),b.end());
k--;
sum=b[n-1]+1-b[0];
for(i=1;i<n;i++)
{
a.push_back(b[i]-b[i-1]-1);
}
sort(a.begin(),a.end());
m=a.size();
for(i=m-1;i>=max(0ll,m-k);i--)
{
sum-=a[i];
}
cout<<sum;
return 0;
}
