#include<bits/stdc++.h>
using namespace std;
using LL = long long;
using ULL = unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)


int main() {

	int N; cin >> N;
	vector<int> B(N); rep(i, N) cin >> B[i];
	sort(B.begin(), B.end());
	rep(i, N) B[i] -= i;
	map<int, int> A;
	rep(i, N) { int a = B[i]; A[a] = A[a] + 1; }
	int ans = 0;
	for (auto p : A) ans = max(ans, p.second);
	cout << ans << endl;

	return 0;
}