#include <iostream>
using namespace std;
const int maxn = 100005;
int idx[maxn];
int sz[maxn];
int n;
void init() {
    for(int i = 0; i < maxn; i++) {
        idx[i] = i;
        sz[i] = 1;
    }
}
int root(int x) {
    while(idx[x] != x) {
        idx[x] = idx[idx[x]];
        x = idx[x];
    }
    return x;
}
void join(int A, int B) {
    int root_A = root(A);
    int root_B = root(B);
    if(root_A != root_B) {
        if(sz[root_A] < sz[root_B]) {
            idx[root_A] = idx[root_B];
            sz[root_B] += sz[root_A];
        }
        else {
            idx[root_B] = idx[root_A];
            sz[root_A] += sz[root_B];
        }
    }
}
bool check(int A, int B) {
    return root(A) == root(B);
}
int main()
{
    cin >> n;
    init();
    vector<int> v(n);
    for(int i = 0; i < n; i++) {
        cin >> v[i];
    }
    
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < n; j++) {
            if(v[i] == v[j] - 1 or v[i] == v[j] + 1) {
                join(i, j);
            }
        }
    }
    int res = 0;
    for(int i = 0; i < n; i++) {
        res = max(res, sz[i]);
    }
    cout << res << endl;
   
    return 0;
}