#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i < (int)(n+1); i++)
#define repn(i,a,b) for (int i = (int)(a) ; i < (int)(b+1); i++)
#define repv(i, n) for (int i = (int)(n-1); i >= 0; i--)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define sz(x) ((int)(x).size())
#define uni(v) v.erase(unique(v.begin(), v.end()), v.end());
using ll = long long;
using P = pair<int,int>;
using mint = modint998244353;
ostream& operator<< (ostream& os, const mint &x) {os << x.val(); return os;}
#ifdef LOCAL
    #include <debug.hpp>
    #define debug(...) debug::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
    #define debug(...) (static_cast<void>(0))
#endif

int main(){
    ll n, k;
    cin >> n >> k;
    vector<ll> a(n);
    rep(i,n) cin >> a[i];
    ll left = 0, right = 1e18;
    ll ans = 0, prev = -1;
    while(ans != prev){
        prev = ans;
        ans = (left + right) / 2;
        ll cnt = 0;
        ll now_plus = 0;
        rep(i,n){
            if(a[i] + now_plus < ans){
                ll now_cnt = (ans - (a[i] + now_plus)) / (i+1);
                if((ans - (a[i] + now_plus)) % (i+1) != 0){
                    now_cnt++;
                }
                cnt += now_cnt;
                now_plus += now_cnt * (i+1);
            }
        }
        if(cnt <= k){
            left = ans;
        }else{
            right = ans;
        }
    }
    cout << ans << endl;
    return 0;
}