#include<bits/stdc++.h>
using namespace std;
#define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define ll long long int
const ll N = 100+5 , INF = 1e18 , MOD = 1e9+7;
void solve(){
ll n,k;
cin >> n >> k;
vector<ll> a(n+5);
for(ll i = 1; i <= n; i++) cin >> a[i];
vector<ll> diff;
for(ll i = 2; i <= n; i++) diff.push_back(a[i]-a[i-1]-1);
sort(diff.begin(),diff.end());
ll ans = n;
for(ll i = 0; i < n-k; i++) ans += diff[i];
cout << ans;
}
int main(){
fast;
ll tc = 1;
// cin >> tc;
while(tc--) solve();
return 0;
}
