#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define int long long
#define all(a) a.begin(),a.end()
#define pb push_back
const int mod = 998244353;
const int maxn = 2 * 1e5 + 7;
void solve(){
int n,k;
cin>>n>>k;
vector <int> a(n),dif(n - 1);
for(int i = 0;i < n;i++){
cin>>a[i];
if(i > 0){
dif[i - 1] = a[i] - a[i - 1] - 1;
}
}
sort(all(dif));
int ans = n;
for(int i = 0;i < (n - k);i++)ans += dif[i];
cout<<ans<<'\n';
}
signed main(){
cin.tie(0) -> sync_with_stdio(0);
int qu;
qu = 1;
while(qu--){
solve();
}
return 0;
}
