#include<bits/stdc++.h> #define REP(i,n) for(int i=0,i##_len=int(n);i<i##_len;++i) #define rep(i,a,b) for(int i=int(a);i<int(b);++i) #define All(x) (x).begin(),(x).end() #define rAll(x) (x).rbegin(),(x).rend() using namespace std; using ll = long long; int main(){ int n,k;cin>>n>>k; vector<ll> a(n); REP(i,n) cin>>a[i]; ll l = *std::min_element(All(a)), r=1e18; while(l+1<r){ ll mid = (l+r)>>1; ll sum = 0; ll fc = 0; REP(i, n){ ll now = a[i] + sum; if(mid - now > 0) { ll cnt = (mid-now + i) / (i+1); sum += cnt * (i+1); fc += cnt; } } if(fc <= k) l = mid; else r = mid; } cout << l << endl; }