#include <bits/stdc++.h>
using namespace std;
#define __Master_Moon__ int main()
#define ll long long
#define el "\n"
#define fi first
#define sq(x) (x)*(x)
#define se second
#define pub push_back
#define puf push_front
#define pii pair <int, int>
#define pll pair <long long, long long>
#define piii pair <int, pair <int, int>>
#define iiii pair <int, pair <int, pair <int, int>>>
#define plll pair <long long, pair <long long, long long>>
#define FOR(i, a, b) for(int i = (a);i <=(b);i++)
#define FO(i, a, b) for(int i = (a);i >= (b);i--)
#define REP(i, n) for(int i = 0;i < (n);i++)
long const maxn = 1e5 + 5;
int n,k,a[maxn],ans;
vector<int> v;
void solve()
{
cin >> n >> k;
k--;
FOR(i,1,n) cin >> a[i];
ans = a[n]-a[1] + 1;
FOR(i,2,n) v.pub(a[i]-a[i-1]-1);
sort(v.begin(),v.end());
FO(i,v.size()-1,max((int)v.size()-k,0))
ans -= v[i];
cout << ans;
}
__Master_Moon__
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
// freopen("o.inp","r",stdin);
// freopen("o.out","w",stdout);
solve();
return 0;
}
