#include <bits/stdc++.h>
using namespace std;

#ifdef CKISEKI
#define safe cerr << __PRETTY_FUNCTION__ << " line " << __LINE__ << " safe\n"
#define debug(a...) debug_(#a, a)
#define orange(a...) orange_(#a, a)
template <typename ...T>
void debug_(const char *s, T ...a) {
    cerr << "\e[1;32m(" << s << ") = (";
    int cnt = sizeof...(T);
    (..., (cerr << a << (--cnt ? ", " : ")\e[0m\n")));
}
template <typename I>
void orange_(const char *s, I L, I R) {
    cerr << "\e[1;32m[ " << s << " ] = [ ";
    for (int f = 0; L != R; ++L)
        cerr << (f++ ? ", " : "") << *L;
    cerr << " ]\e[0m\n";
}
#else
#define safe ((void)0)
#define debug(...) ((void)0)
#define orange(...) ((void)0)
#endif

template <typename T>
using min_heap = priority_queue<T, vector<T>, greater<T>>;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, m, k;
    cin >> n >> m >> k;

    vector<int64_t> a(n), p(n + 1);

    vector<int> tag(n + 1);

    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    for (int i = 0; i < n; i++) {
        p[i + 1] = p[i] + a[i];
    }

    vector<vector<pair<int,int64_t>>> g(n + 1);
    const auto check = [&](int l, int r) {
        if (p[r] - p[l] >= k) {
            g[l].emplace_back(r, p[r] - p[l] - k);
            debug(l, r, p[r]-p[l]-k);
        } else {
            tag[l] += 1;
            tag[r] -= 1;
        }
    };

    for (int i = 0; i < m; i++) {
        check(0, i + 1);
        check(n - i - 1, n);
    }

    for (int i = 0; i + m <= n; i++) {
        check(i, i + m);
    }

    for (int i = 1; i <= n; i++) {
        tag[i] += tag[i - 1];
    }

    orange(tag.begin(), tag.end());

    for (int i = 0; i < n; i++) {
        if (tag[i] == 0) {
            g[i].emplace_back(i + 1, a[i]);
            g[i + 1].emplace_back(i, 0);
        } else {
            g[i].emplace_back(i + 1, 0);
            g[i + 1].emplace_back(i, 0);
        }
    }
    
    vector<int64_t> dis(n + 1, 1e18);
    vector<int> vis(n + 1);
    min_heap<pair<int64_t,int>> pq;
    pq.emplace(0, 0);
    dis[0] = 0;
    while (!pq.empty()) {
        auto [_, i] = pq.top(); pq.pop();
        if (vis[i]) continue;
        vis[i] = true;
        for (auto [j, w]: g[i]) {
            if (dis[j] > dis[i] + w)
                dis[j] = dis[i] + w, pq.emplace(dis[j], j);
        }
    }

    debug(dis[n], p[n]);
    cout << p[n] - dis[n] << '\n';


    return 0;
}