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

#define int int64_t

const int maxn = 2e5 + 87;

int f[maxn] = {}, dis[maxn] = {};
vector<pair<int, int>> G[maxn];
int n, m, k;
    

void solve() {
    cin >> n >> m >> k;
    for(int i = 1; i <= n; ++i) {
        cin >> f[i];
    }
    for(int i = 1; i <= n; ++i) {
        f[i] += f[i - 1];
    }
    for(int i = 1; i <= n; ++i) {
        G[i].emplace_back(i - 1, f[i] - f[i - 1]); // s[i] - s[i - 1] <= f[i]
        G[i - 1].emplace_back(i, 0); // s[i] - s[i - 1] >= 0
    }
    for(int i = 1; i <= n; ++i) {
        int p = max(i - m, int(0));
        int d = min(k, f[i] - f[p]);
        G[p].emplace_back(i, -d); // s[i] - s[p] >= d
    }
    for(int i = 1; i < m; ++i) {
        int p = max(n - m + i, int(0));
        int d = min(k, f[n] - f[p]);
        G[p].emplace_back(n, -d);  // s[n] - s[p] >= d
    }
    // min distance
    priority_queue<pair<int, int>> pq;
    memset(dis, 0x3f, sizeof(dis));
    dis[0] = 0;
    pq.emplace(dis[0], 0);
    while(pq.size()) {
        int x = pq.top().second;
        int d = -pq.top().first;
        pq.pop();
        if(dis[x] != d) continue;
        for(auto e : G[x]) {
            if(dis[e.first] > dis[x] + e.second) {
                dis[e.first] = dis[x] + e.second;
                pq.emplace(-dis[e.first], e.first);
            }
        }
    }
    cout << -dis[n] << '\n';
}

int32_t main() {
    ios_base::sync_with_stdio(0), cin.tie(0);
    
    solve();
    
    return 0;
}