#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
void solve() {
}
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N;
	long long K;
	cin >> N >> K;
	vector<long long> A(N);
	for( int i = 0; i < N; i++ ) {
		cin >> A[i];
	}
	long long l = 0, r = 1LL<<60, m;
	while( r-l > 1 ) {
		m = (l+r)>>1;
		long long s = 0, k = 0;
		for( long long i = 0; i < N; i++ ) {
			long long x = max(0LL, m-(A[i]+s));
			k += (i+x)/(i+1);
			s += (i+x)/(i+1)*(i+1);
		}
		if( k <= K ) {
			l = m;
		}else {
			r = m;
		}
	}
	cout << l << endl;
}