#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll,ll>;
#define fix(x) fixed << setprecision(x)
#define asc(x) x, vector<x>, greater<x>
#define rep(i, n) for(ll i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}
constexpr ll INFLL = (1LL << 62), MOD = 998244353;
constexpr int INF = (1 << 30);

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    ll n,k;
    cin >> n >> k;
    vector<ll> a(n);
    rep(i,n) cin >> a[i];
    ll ok = 0, ng = 1e15;
    while(ng-ok>1){
        ll md = (ng+ok)/2, tot = 0, x = 0;
        rep(i,n){
            ll z = max((md-a[i]-tot+i)/(i+1), 0LL);
            tot += z * (i+1);
            x += z;
        }
        if(x<=k) ok = md;
        else ng = md;
    }
    cout << ok << '\n';
    return 0;
}