///TRAN THAI BAO :3
#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
#define maxN 100007
vector<int>gap;
int n, k;
int t[maxN];
void readData()
{
cin >> n >> k;
for(int i = 1; i <= n; i++)
cin >> t[i];
}
void solve()
{
int ans = n;
for(int i = 2; i <= n; i++)
gap.push_back(t[i] - t[i-1]-1);
sort(gap.begin(), gap.end());
int j = 0;
while(n > k)
{
ans += gap[j++];
n--;
}
cout << ans;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
readData();
solve();
return 0;
}
