#include <iostream>
#include <vector>

int main() {
    int n, k;
    std::cin >> n >> k;
    std::vector<long long> a(n);
    for (int i = 0; i < n; i++) {
        std::cin >> a[i];
    }

    auto check = [&](long long key) -> bool {
        long long sum = 0;
        long long count = 0;
        for (int i = 0; i < n; i++) {
            if (a[i] + sum < key) {
                long long temp = (key - (sum + a[i]) + i) / (i + 1);
                sum += temp * (i + 1);
                count += temp;
            }
            if (count > k) {
                return false;
            }
        }
        return true;
    };

    long long ok = 0;
    long long ng = 1e15;
    while (ng - ok > 1) {
        long long key = (ok + ng) / 2;
        if (check(key)) {
            ok = key;
        } else {
            ng = key;
        }
    }
    std::cout << ok << '\n';
}