#include <bits/stdc++.h>
#define be(v) (v).begin(),(v).end()
#define pb(q) push_back(q)
#define rep(i, n) for(int i=0;i<n;i++)
#define all(i, v) for(auto& i : v)
typedef long long ll;
using namespace std;
const ll mod=1000000007, INF=(1LL<<60);
#define doublecout(a) cout<<fixed<<setprecision(10)<<a<<endl;

int main() {
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(false);
    ll n, k;
    cin >> n >> k;
    vector<ll> a(n + 1);
    rep(i, n) cin >> a[i + 1];
    ll le = 0, ri = 10000000LL * 20000001LL;
    while(ri - le > 1LL) {
        ll mid = (ri + le) / 2;
        ll num = 0;
        ll sum = 0;
        bool ng = false;
        for(ll i = 1; i <= n; i ++) {
            ll nn = (mid - a[i] - sum + i - 1) / i;
            if(nn <= 0) continue;
            // if(mid == 5)cout << i << "  " << nn << endl;
            num += nn;
            sum += nn * i;

            // if(mid == 5)cout << num << " " << k << endl;
            if(num > k) {
                ng = true;
                break;
            }
        }
        if(ng) ri = mid;
        else le = mid;
    }
    cout <<le << endl;
    return 0;
}