#include <bits/stdc++.h>

using namespace std;

const int N = 210000, M = 2100000;

int n, m;

long long k;

long long a[N];

long long b[N];

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

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


    long long cur_sum = 0;
    deque<int> q;

    for (int i = 1; i <= n + m - 1; i ++) {
        while (q.front() <= i - m) {
            q.pop_front();
        }

        if (i - m > 0) {
            cur_sum -= b[i - m];
        }

        if (i <= n) {
            q.push_back(i);
        }


        while (!q.empty() && cur_sum < k) {
            int j = q.back();
            q.pop_back();

            if (cur_sum + a[j] - b[j] >= k) {
                b[j] += k - cur_sum;
                cur_sum = k;

                if (b[j] < a[j]) q.push_back(j);
            }

            else {
                cur_sum += (a[j] - b[j]);
                b[j] = a[j];
            }


        }
    }

    long long ans = 0;
    for (int i = 1; i <= n; i ++) {
        //cout << i << " : " << b[i] << "\n";
        ans += b[i];
    }

    cout << ans;


    return 0;
}