#include<bits/stdc++.h>
using namespace std;
using ll=long long;
#define rep(i,n) for(int i=0;i<n;i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
template<class T> bool chmax(T &a, T b){if (a < b){a = b;return true;} else return false;}
template<class T> bool chmin(T &a, T b){if (a > b){a = b;return true;} else return false;}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int 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 mid=(ok+ng)/2;
        ll cnt=0,t=0;
        vector<ll>B(n);
        rep(i,n)B[i]=A[i];
        rep(i,n){
            if(B[i]+t<mid){
                cnt+=(mid-B[i]-t+i)/(i+1);
                t+=(i+1)*((mid-B[i]-t+i)/(i+1));
            }
        }
        if(cnt<=k)ok=mid;
        else ng=mid;
    }
    cout<<ok<<"\n";
}