#include <bits/stdc++.h>
#include <cassert>
#include <cmath>
#include <complex>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
#define all(A) A.begin(),A.end()
#define rep(i, n) for (ll i = 0; i < (ll) (n); i++)
template<class T>
bool chmax(T& p, T q, bool C = 1) {
    if (C == 0 && p == q) {
        return 1;
    }
    if (p < q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}

template<class T>
bool chmin(T& p, T q, bool C = 1) {
    if (C == 0 && p == q) {
        return 1;
    }
    if (p > q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}

ll gcd(ll(a), ll(b)) {
    if (a == 0)return b;
    if (b == 0)return a;
    ll c = a;
    while (a % b != 0) {
        c = a % b;
        a = b;
        b = c;
    }
    return b;
}
ll sqrtz(ll N) {
    ll L = 0;
    ll R = sqrt(N) + 10000;
    while (abs(R - L) > 1) {
        ll mid = (R + L) / 2;
        if (mid * mid <= N)L = mid;
        else R = mid;
    }
    return L;

}


using mint = modint998244353;

int main() {

    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll N,K;
    cin>>N>>K;
    vll A(N);

    rep(i,N){
        cin>>A[i];
    }
    ll L=0,R=1e18;
    while(R-L>1){
        ll M=(R+L)/2;
        ll P=0;
        vll D=A;
        ll k=0;
        rep(i,N){
            D[i]+=P;
            if(D[i]<M){
                ll p=(M-D[i]+i)/(i+1);
                k+=p;
                P+=p*(i+1);
            }
        }
        (k<=K?L:R)=M;
    }
    cout<<L<<endl;
}