#include <iostream>
#include <array>

int main(int argc, char* argv[]) {
    int n;
    std::cin >> n;

    std::array<int, 101> count;
    for (int i = 0; i < 101; i++)
        count[i] = 0;

    for (int i = 0; i < n; i++) {
        int a;
        std::cin >> a;
        count[a]++;
    }

    int max = 0;

    for (int i = 1; i < 101; i++) {
        max = std::max(max, count[i - 1] + count[i]);
    }

    std::cout << max << "\n";
}