#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }


int N, M;
Int K;
vector<Int> F;

int main() {
  for (; ~scanf("%d%d%lld", &N, &M, &K); ) {
    F.resize(N);
    for (int i = 0; i < N; ++i) {
      scanf("%lld", &F[i]);
    }
    
    const int L = N - 1 + M;
    vector<Int> pay(L, 0);
    Int now = 0;
    int len = 0;
    vector<pair<int, Int>> stack(N);
    for (int i = 0; i < L; ++i) {
      // condition for (i - M, i]
      if (i - M >= 0) {
        now -= pay[i - M];
      }
      if (i < N) {
        stack[len++] = make_pair(i, F[i]);
      }
      for (; now < K && len > 0; --len) {
        const int j = stack[len - 1].first;
        Int &f = stack[len - 1].second;
        if (i - M < j) {
          const Int t = min(f, K - now);
          pay[j] += t;
          now += t;
          f -= t;
          if (f > 0) {
            break;
          }
        }
      }
    }
// cerr<<"pay = "<<pay<<endl;
    
    Int ans = 0;
    for (int i = 0; i < L; ++i) {
      ans += pay[i];
    }
    printf("%lld\n", ans);
  }
  return 0;
}