#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int,int> P;
#define REP(i,n) for(int i=0;i<int(n);i++)

ll a[100010],N,K,KK;
bool check(ll x){
	ll c=0;
	K=KK;
	for(ll i=1;i<=N;i++){
		if(a[i]+c>=x) continue;
		else{
			ll k=(x-a[i]-c+i-1)/i;
			if(K-k>=0){
				K-=k;
				c+=k*i;
			}
			else return false;
		}
	}

	return true;
}

int main(void){
	cin.tie(nullptr);  ios_base::sync_with_stdio(false);
	ll i,j,k;

	cin >> N >> KK;
	for(i=1;i<=N;i++) cin >> a[i];

	ll ok=-1,ng=1e15;
	while(ng-ok>1){
		ll mid=(ok+ng)/2;
		if(check(mid)) ok=mid;
		else ng=mid;
	}

	cout << ok << endl;

	return 0;
}