//#pragma GCC optimize("Ofast", "unroll-loops")
//#pragma GCC target("sse", "sse2", "sse3", "ssse3", "sse4")

#ifdef __APPLE__

#include <iostream>
#include <cmath>
#include <algorithm>
#include <stdio.h>
#include <cstdint>
#include <cstring>
#include <string>
#include <cstdlib>
#include <vector>
#include <bitset>
#include <map>
#include <queue>
#include <ctime>
#include <stack>
#include <set>
#include <list>
#include <random>
#include <deque>
#include <functional>
#include <iomanip>
#include <sstream>
#include <fstream>
#include <complex>
#include <numeric>
#include <cassert>
#include <array>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <thread>

#else
#include <bits/stdc++.h>
#endif

#define all(a) a.begin(),a.end()
#define len(a) (int)(a.size())
#define mp make_pair
#define pb push_back
#define fir first
#define sec second
#define fi first
#define se second

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
typedef long double ld;

template<typename T>
bool umin(T &a, T b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}

template<typename T>
bool umax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

#if __APPLE__
#define D for (bool _FLAG = true; _FLAG; _FLAG = false)
#define LOG(...) print(#__VA_ARGS__" ::", __VA_ARGS__) << endl

template<class ...Ts>
auto &print(Ts ...ts) { return ((cerr << ts << " "), ...); }

#else
#define D while (false)
#define LOG(...)
#endif

const int max_n = 6e5 + 42, inf = 1000111222;

//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

template<typename T>
struct segment_tree {
    T f[4 * max_n];
    T mn[4 * max_n];

    void build(int v, int l, int r) {
        f[v] = 0;
        if (l == r) {
            mn[v] = 0;
            return;
        }
        int mid = (l + r) / 2;
        build(2 * v, l, mid);
        build(2 * v + 1, mid + 1, r);
        mn[v] = min(mn[2 * v], mn[2 * v + 1]);
    }

    void push(int v, int l, int r, int mid) {
        if (f[v]) {
            mn[2 * v] += f[v];
            mn[2 * v + 1] += f[v];
            f[2 * v] += f[v];
            f[2 * v + 1] += f[v];
            f[v] = 0;
        }
    }

    void update(int v, int tl, int tr, int l, int r, T value) {
        if (tl == l && tr == r) {
            f[v] += value;
            mn[v] += value;
            return;
        }
        int mid = (tl + tr) / 2;
        push(v, tl, tr, mid);
        if (r <= mid) {
            update(2 * v, tl, mid, l, r, value);
        } else if (l > mid) {
            update(2 * v + 1, mid + 1, tr, l, r, value);
        } else {
            update(2 * v, tl, mid, l, mid, value);
            update(2 * v + 1, mid + 1, tr, mid + 1, r, value);
        }
        mn[v] = min(mn[2 * v], mn[2 * v + 1]);
    }

    T get_min(int v, int tl, int tr, int l, int r) {
        if (tl == l && tr == r) {
            return mn[v];
        }
        int mid = (tl + tr) / 2;
        push(v, tl, tr, mid);
        if (r <= mid) {
            return get_min(2 * v, tl, mid, l, r);
        } else if (l > mid) {
            return get_min(2 * v + 1, mid + 1, tr, l, r);
        }
        return min(get_min(2 * v, tl, mid, l, mid), get_min(2 * v + 1, mid + 1, tr, mid + 1, r));
    }
};

void solve() {
    ll n, m, k;
    cin >> n >> m >> k;
    vector<ll> a;
    for(int i = 1; i < m; i++) a.pb(0);
    for(int i = 0; i < n; i++) {
        int x = 1; 
        cin >> x;
        a.pb(x);
    }
    for(int i = 1; i < m; i++) a.pb(0);
    segment_tree<ll> st = {}; st.build(1, 0, max_n - 1);
    for(int i = m - 1; i < len(a); i++) st.update(1, 0, max_n - 1, i - m + 1, i, a[i]);
//    for(int i = 0; i + m - 1 < len(a); i++) cout << st.get_min(1, 0, max_n - 1, i, i) << ' ';
//    cout << '\n';
    for(int i = m - 1; i < len(a); i++) {
        ll cr = st.get_min(1, 0, max_n - 1, i - m + 1, i);
//        cout << cr << ' ';
        ll have = a[i];
        ll to_del = max(0ll, min(have, cr - k));
//        cout << to_del << '\n';
        a[i] -= to_del;
        st.update(1, 0, max_n - 1, i - m + 1, i, -to_del);
//        for(int i = 0; i + m - 1 < len(a); i++) cout << st.get_min(1, 0, max_n - 1, i, i) << ' ';
//        cout << '\n';
    }
    ll ans = 0;
    for(auto& x : a) {
        ans += x;
//        cout << x << ' ';
    }
//    cout << '\n';
    cout << ans << '\n';
}

signed main() {
//   freopen("input.txt", "r", stdin);
//   freopen("output.txt", "w", stdout);

    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int t = 1;

    //cin >> t;

    while (t--) solve();

}

/*
KIVI
*/