#include<bits/stdc++.h>
#include<atcoder/all>
#define chmin(x,y) (x) = min((x),(y))
#define chmax(x,y) (x) = max((x),(y))
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define vec vector
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back 
#define eb emplace_back

using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
const ll mod = 998244353;
using mint = modint998244353;
const vector<int> dx = {1,0,-1,0}, dy = {0,1,0,-1};
// using Graph = vector<vector<pair<int,ll>>>;
using Graph = vector<vector<int>>;

int main(){
  // input
  int N,K; ll X;
  cin >> N >> K >> X;
  vec<ll> A(N);
  rep(i,N) cin >> A[i];

  // solve
  priority_queue<ll> pq;
  ll sum = 0, ans = -9e18;
  rep(i,N){
    pq.push(-A[i]);
    sum += A[i];
    if(pq.size() > K){
      sum += pq.top();
      pq.pop();
    }
    ll tmp = sum - X * (i+1);
    // cout << i << " " << tmp << endl;
    chmax(ans, tmp);
  }

  // output
  cout << ans << endl;
}