#include <bits/stdc++.h>
#define endl '\n'
#define int long long
#pragma GCC optimize("O2")
using namespace std;
int32_t main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cout.precision(0);
cout<<fixed;
int n,k;
cin>>n>>k;
vector<int> x(n);
for (int i = 0; i < n; i++)
{
cin>>x[i];
}
vector<int> dp(k);
int res=x[n-1]+1-x[0];
//cout<<res<<endl;
vector<int> vs;
for (int i = 1; i < n; i++)
{
vs.push_back(x[i]-x[i-1]);
}
sort(vs.begin(),vs.end());
for (int j = 2; j <= k; j++)
{
res-=vs.back()-1;
vs.pop_back();
}
cout<<res<<endl;
return 0;
}
