#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
using namespace std;

typedef long long ll;


bool check_k0(int x, int n, int m, const vector<int> &a) {
    ll operations_needed = 0;
    vector<ll> diff(n + 2, 0);
    ll current = 0;
    for(int j=1; j<=n; ++j){
        current += diff[j];
        if(current < a[j-1]){
            ll need = a[j-1] - current;
            operations_needed += need;
            if(operations_needed > m) return false;
            int s = min(j + x, n);
            diff[j] += need;
            diff[s +1] -= need;
            current += need;
        }
    }
    return operations_needed <= m;
}


bool check_k1(int x, int n, int m, const vector<int> &a){
    ll max_required_x = 0;
    for(int j=1; j<=n; ++j){
        
        ll required = ( (ll)a[j-1] + m -1 ) / m + j -1;
        if(x < required){
            return false;
        }
    }
    return true;
}


bool check_k2(int x, int n, int m, const vector<int> &a){
    ll operations_needed = 0;
    
    vector<ll> add(n + 2, 0);
    vector<ll> dec(n + 2, 0);
    ll current_sum = 0;
    for(int j=1; j<=n; ++j){
        current_sum += add[j];
        if(j > x){
            current_sum -= dec[j];
        }
        if(current_sum < a[j-1]){
            ll need = a[j-1] - current_sum;
            operations_needed += need;
            if(operations_needed > m) return false;
            
            add[j] += need * (ll)x;
            if(j + x <= n){
                dec[j + x] += need;
            }
            current_sum += need * (ll)x;
        }
    }
    return operations_needed <= m;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    int n, m, k;
    cin >> n >> m >> k;
    vector<int> a(n);
    for(auto &x : a) cin >> x;
    
    
    int left = 0, right = 200000; 
    int answer = -1;
    while(left <= right){
        int mid = left + (right - left)/2;
        bool feasible = false;
        if(k ==0){
            feasible = check_k0(mid, n, m, a);
        }
        else if(k ==1){
            feasible = check_k1(mid, n, m, a);
        }
        else if(k ==2){
            feasible = check_k2(mid, n, m, a);
        }
        if(feasible){
            answer = mid;
            right = mid -1;
        }
        else{
            left = mid +1;
        }
    }
    cout << answer;
}