// I love Manuela
#include<bits/stdc++.h>
#define pb push_back
#define ll long long
using namespace std;

const ll iden = LLONG_MAX;

struct node {
	node *left = nullptr, *right = nullptr;
	ll val = 1e18, lazy = 0;
	node() {}
};

void innit(node *now, int lo, int hi, vector<ll> &vals){
	if(lo > hi) return;
	if(lo == hi){
		now->val = vals[lo];
		return;
	}
	int mid = (lo+hi)>>1;
	now-> left = new node();
	now->right = new node();
	innit(now->left,lo,mid,vals);
	innit(now->right,mid+1,hi,vals);
	now->val = min(now->left->val,now->right->val);
}

void push(node *v){
	if(!v->lazy) return;

	v->right->lazy += v->lazy;
	v->right->val += v->lazy;

	v->left->lazy += v->lazy;
	v->left->val += v->lazy;

	v->lazy = 0;
}

void update(node *v, ll low, ll high, ll l, ll r, ll value){
	if(l > high || r < low || low > high) return;
	if(low >= l && high <= r){
		v->val += value;
		v->lazy += value;
		return;
	}
	ll mid = (low+high)>>1;
	push(v);
	if(l <= mid)
		update(v->left,low,mid,l,r,value);
	if(r > mid)
		update(v->right,mid+1,high,l,r,value);
	v->val = min(v->left->val,v->right->val);
}

ll query_min(node *v, ll low, ll high, ll l, ll r){
	if(l > high || r < low || low > high) return iden;
	if(low >= l && high <= r) return v->val;
	ll mid = (low+high)>>1;
	push(v);
	ll v1 = query_min(v->left,low,mid,l,r);
	ll v2 = query_min(v->right,mid+1,high,l,r);
	return min(v1,v2);
}

int main(){
	ios_base::sync_with_stdio(0),cin.tie(0);
	ll n,m,k; cin >> n >> m >> k;
	vector<ll> vals(n);
	for(auto &va:vals)
		cin >> va;

    vector<ll> temp;
    for(int i = 0; i < m-1;++i) temp.pb(0);
    for(int i = 0; i < n;++i) temp.pb(vals[i]);
    for(int i = 0; i < m-1;++i) temp.pb(0);
    
    vals = temp;
    n = vals.size();
    
    vector<ll> sums(n);
	for(int i = 0; i < n;++i){
		sums[i] = vals[i];
		if(i) sums[i] += sums[i-1];
	}
    
	vector<ll> imp(n);
	for(int i = 0; i < n;++i){
		if(i + m - 1 < n){
			imp[i] = sums[i+m-1];
			if(i-1 > -1) imp[i] -= sums[i-1];
		} else imp[i] = LLONG_MAX;
	}

	node *st = new node();
	ll low = 0, high = imp.size()-1;
	innit(st,low,high,imp);

	ll ans = 0;

	for(int i = n-1;i > -1;--i){
		int l = max(0LL,i-m+1);
		ll mi = max(query_min(st,low,high,l,i) - k,0LL);
		mi = min(mi,vals[i]);
		ans += mi;
		update(st,low,high,l,i,-mi);
	}

	cout << sums.back() - ans << '\n';

	return 0;
}