#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pll;
#define fastio ios::sync_with_stdio(false), cin.tie(0)
#define pb push_back
#define eb emplace_back
#define f first
#define s second
#define lowbit(x) x&-x
const int maxn = 2e5 + 5;
signed main(void){
fastio;
int n, k;
cin>>n>>k;
vector<int> a(n);
for(int i = 0; i < n; i++) cin>>a[i];
int ans = n;
vector<int> val;
for(int i = 1; i < n; i++) val.pb(a[i] - a[i - 1] - 1);
sort(val.begin(), val.end());
int use = n - k;
for(int i = 0; i < use; i++) ans += val[i];
cout<<ans<<"\n";
}
