#include <bits/stdc++.h>
#define fi first
#define se second
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = 1; i <= (n); ++i)
#define drep(i, n) for (int i = (n)-1; i >= 0; --i)
#define srep(i, s, t) for (int i = s; i < (t); ++i)
#define dsrep(i, t, s) for (int i = (t)-1; i >= (s); --i)
#define rng(a) a.begin(), a.end()
#define rrng(a) a.rbegin(), a.rend()
#define isin(x, l, r) ((l) <= (x) && (x) < (r))
#define pb push_back
#define eb emplace_back
#define sz(x) (int)(x).size()
using namespace std;
using ll = long long;
template <typename T>
using vc = vector<T>;
template <typename T>
using vv = vc<vc<T>>;
template <typename T>
using vv = vc<vc<T>>;
using vl = vc<ll>;
using vvl = vv<ll>;
using vvvl = vv<vl>;
typedef pair<ll, ll> P;
const int INF = 1001001001;
const ll LINF = 1001002003004005006ll;
template <class T>
inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}
#define dame        \
    {               \
        puts("-1"); \
        return;     \
    }
#define yes          \
    {                \
        puts("Yes"); \
        return;      \
    }
#define no          \
    {               \
        puts("No"); \
        return;     \
    }
#define ret(x)               \
    {                        \
        cout << (x) << endl; \
        return;              \
    }
#define yn           \
    { puts("Yes"); } \
    else {           \
        puts("No");  \
    }
const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};

int main() {
    ll n, k;
    cin >> n >> k;
    vl a(n);
    rep(i, n) cin >> a[i];
    ll l = -1;
    ll r = 1e15;
    auto f = [&](ll x) -> bool {
        ll cnt = 0;
        ll tmp = 0;
        rep(i, n) {
            if (a[i] + tmp >= x) continue;
            ll ttmp = (x - a[i] + i - tmp) / (i + 1);
            cnt += ttmp;
            tmp += ttmp * (i + 1);
        }
        return cnt <= k;
    };
    while (r - l > 1) {
        ll mid = (l + r) / 2;
        if (f(mid))
            l = mid;
        else
            r = mid;
    }
    cout << l << endl;
}