#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main() {
int n;
cin >> n;
vector<int> v(n);
for (int i = 0; i < n; i++)
cin >> v[i];
sort(v.begin(), v.end());
int len = 0, count = 1, first = v[0];
for (int i = 1; i < v.size(); i++) {
if (first == v[i] || first + 1 == v[i])
count++;
else {
if (count > len)
len = count;
count = 1;
first = v[i];
}
}
cout << max(len, count) << endl;
return 0;
}
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