#include <bits/stdc++.h>
#define en cin.close();return 0;
using namespace std;

typedef long long ll;
typedef pair<int, int> pii;

#define fi first
#define se second
#define mp make_pair
#define pb push_back

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
//    ifstream cin("in.in");
    ll n, m, k;
    cin >> n >> m >> k;
    set<ll> s;
    ll f[n+1], taken[n+1];
    memset(taken,0,sizeof(taken));
    for(ll i = 1;i<=n;i++)
    {
        cin >> f[i];
        s.insert(i);
    }
    ll res = 0;
    ll cur = 0;
    for(ll i = n;i>0;i--)
    {
        if(i+m<=n)
            cur-=taken[i+m];
        while(cur<k)
        {
            auto t = s.lower_bound(i);
            if(t==s.end())
                break;
            ll pos = *t, need = k-cur, take = min(need,f[pos]-taken[pos]);
            taken[pos]+=take;
            cur+=take;
            res+=take;
            if(f[pos]==taken[pos])
                s.erase(pos);
        }
    }
    cur = 0;
    for(ll i = 0;i<n&&cur<k;i++)
    {
        if(cur+f[i]<=k)
            res+=f[i]-taken[i];
        else
        {
            ll need = k-cur;
            if(need>taken[i])
                res+=need-taken[i];
        }
        cur+=f[i];
    }
    cout << res;
    return 0;
}