#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define pii pair<int,int>
#define sz size()
#define all(v) v.begin(),v.end()
#define fi first
#define se second
const int N = 2e5;
const int mod = 1e9+7;
const ll INF = 1e18;
const int di[] = {1, -1, 0, 0};
const int dj[] = {0, 0, 1, -1};
void solve() {
int n,k;
cin>>n>>k;
ll a[n+1];
for(int i = 1; i <= n; i++){
cin>>a[i];
}
ll ans=a[n]-a[1]+k;
vector<ll> v;
for(int i = 2; i <= n; i++){
v.pb(a[i]-a[i-1]);
}
sort(v.rbegin(),v.rend());
for(int i = 0; i < k-1; i++){
ans-=v[i];
}
cout<<ans<<"\n";
}
int main() {
//freopen("cowrun.in","r",stdin);
//freopen("cowrun.out","w",stdout);
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int t=1;
//cin>>t;
while(t--) {
solve();
}
return 0;
}
