//  Nikita Golikov, 2023

#include <bits/stdc++.h>

using namespace std;

using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;

#ifdef GOLIKOV
  #include "/Users/golikovnik/contests/debug.h"
#else
  #define debug(...) ;
#endif

template <class A, class B>
bool smin(A& x, B&& y) {
  if (y < x) {
    x = y;
    return true;
  }
  return false;
}

template <class A, class B>
bool smax(A& x, B&& y) {
  if (x < y) {
    x = y;
    return true;
  }
  return false;
}

int main() {
#ifdef GOLIKOV
  assert(freopen("in", "rt", stdin));
  auto _clock_start = chrono::high_resolution_clock::now();
#endif
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int n, m, k;
  cin >> n >> m >> k;
  vector<ll> a(n);
  for (auto& x : a) cin >> x;
  vector<ll> cnt(n);
  ll cur = 0;
  set<int> notFull;
  for (int i = 0; i < n; ++i) {
    notFull.insert(i);
  }
  for (int i = 0; i - (m - 1) < n; ++i) {
    debug(i, cur);
    while (cur < k) {
      auto it = notFull.upper_bound(i);
      if (it != notFull.begin()) {
        --it;
        int j = *it;
        ll use = min(k - cur, a[j] - cnt[j]);
        cnt[j] += use;
        cur += use;
        if (cnt[j] == a[j]) {
          notFull.erase(j);
        }
      } else {
        break;
      }
    }
    debug(cur);
    if (i >= m - 1) {
      cur -= cnt[i - (m - 1)];
    }
  }
  debug(cnt);
  cout << accumulate(cnt.begin(), cnt.end(), 0ll) << '\n';

#ifdef GOLIKOV
  cerr << "Executed in " << chrono::duration_cast<chrono::milliseconds>(
      chrono::high_resolution_clock::now()
          - _clock_start).count() << "ms." << endl;
#endif
  return 0;
}