#define rep(i, l, r) for (auto i = (l); i < (r); i++)
#define chmax(dest, src) if ((dest) < (src)) dest = (src)
#define chmin(dest, src) if ((dest) > (src)) dest = (src)
#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> A(N);
  rep(i, 0, N) cin >> A[i];
  sort(A.begin(), A.end());
  int count = 1;
  int c = 1;
  int prev = 0;
  for_each(A.begin(), A.end(), [&](int a) {
     if (prev + 1 >= a) {
         c++;
     } else {
         chmax(count, c);
         c = 1;
     }
     prev = a;
  });
  cout << count;
  return 0;
}