#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <iterator>

namespace {
  
size_t FindMaxSeqLen(const std::vector<size_t>& nums) {
  size_t max_seq_len = 1;
  size_t seq_len = 1;
  size_t start_indx = 0;
  for (size_t i = 1; i < nums.size(); ++i) {
    if (nums.at(i) - nums.at(start_indx) <= 1) {
      ++seq_len;
      continue;
    }
    max_seq_len = std::max(max_seq_len, seq_len);
    seq_len = 1;
    start_indx = i;
  }
  return std::max(max_seq_len, seq_len);
}
  
} // end of <anonymous> namespace

int main() {
  size_t n;
  std::vector<size_t> nums;
  std::cin >> n;
  std::copy_n(std::istream_iterator<size_t>(std::cin), n, std::back_inserter(nums));
  std::sort(nums.begin(), nums.end());
  std::cout << FindMaxSeqLen(nums);
  return 0;
}