#include <bits/stdc++.h>
using namespace std;
using ull = uint64_t;
using ll = int64_t;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define N4(f)	\
f(0,1)	\
f(0,-1)	\
f(1,0)	\
f(-1,0)
#define N8(f)	\
f(y+1,x+1)	\
f(y+1,x+0)	\
f(y+1,x-1)	\
f(y+0,x+1)	\
f(y+0,x-1)	\
f(y-1,x+1)	\
f(y-1,x+0)	\
f(y-1,x-1)
#define N9(f)	\
f(y+1,x+1)	\
f(y+1,x+0)	\
f(y+1,x-1)	\
f(y+0,x+1)	\
f(y+0,x+0)	\
f(y+0,x-1)	\
f(y-1,x+1)	\
f(y-1,x+0)	\
f(y-1,x-1)

signed main() {
	int n,k,x;cin>>n>>k>>x;
	vector<ll> a(n);
	rep(i,n)cin>>a[i];
	ll ans=-1e12;
	multiset<ll> ms;
	ll sum=0;
	rep(i,k)ms.insert(0);
	rep(i,n) {
		if (a[i]>=*ms.begin()) {
			ms.insert(a[i]);
			sum+=a[i]-*ms.begin();
			ms.erase(ms.begin());
			ans=max(ans,sum-(i+1)*x);
		}
	}
	cout<<ans<<endl;
}