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

long long a[400009], ans, lf[400009], org_a[400009];

int main(){
    ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0);
    int n, m, k;
    cin >> n >> m >> k;

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

    long long sum = k;
    for(int i = 1; i <= n + m - 1; i++){
        int j = i;
        while(sum > 0 && j > i - m){
            if(a[j] > sum){
                a[j] -= sum;
                ans += sum;
                sum = 0;
                break;
            }

            sum -= a[j];
            ans += a[j];
            a[j] = 0;
            lf[i] = lf[j - 1];
            j = lf[j - 1];
        }

        //cout << i << " " << ans << endl;
        if(i - m + 1 >= 1) sum += org_a[i - m + 1] - a[i - m + 1];
    }

    cout << ans;
    return 0;
}