#include<bits/stdc++.h>// <3 Nandini <3
using namespace std;
#define gc getchar
#define mp make_pair
#define pb push_back
#define sc scanint
#define dc print_int
#define f first
#define s second
#define ret return 0;
#define rf std::ios::sync_with_stdio(false);
#define mi 1000000007
#define tl int t;sc(t);while(t--)
#define in int n;sc(n);
#define vin vi arr; for(int i=0;i<n;i++){int a;sc(a);arr.pb(a);}
#define st string s1; getline(cin>>ws,s1);
#define sorta sort(arr.begin(),arr.end());
#define reva reverse(arr.begin(),arr.end());
#define pf(a) printf("%d",a);
#define mina *min_element(arr.begin(),arr.end())
#define maxa *max_element(arr.begin(),arr.end())
#define sl scanlong
typedef vector<int> vi;
typedef vector<pair<int,int> > vii;
typedef long long int ll;
typedef pair<int, int> pii;
typedef unsigned long long int ull;


void scanint(int &x)
{
    register int c = gc();
    x = 0;
    int neg = 0;
    for(;((c<48 || c>57) && c != '-');c = gc());
    if(c=='-') {neg=1;c=gc();}
    for(;c>47 && c<58;c = gc()) {x = (x<<1) + (x<<3) + c - 48;}
    if(neg) x=-x;
}
void scanlong(ull &x);
void scanlong(ull &x)
{
        int flag=0;
        register int c = gc();
        if(c == '-') flag=1;
	x = 0;
	for(;(c<48 || c>57);c = gc());
	for(;c>47 && c<58;c = gc()) {x = (x<<1) + (x<<3) + c - 48;}
        if(flag == 1)x=-x;
}
int lis( int arr[], int n )
{
    int *lis, i, j, max = 0;
    lis = (int*) malloc ( sizeof( int ) * n );

    /* Initialize LIS values for all indexes */
    for (i = 0; i < n; i++ )
        lis[i] = 1;

    /* Compute optimized LIS values in bottom up manner */
    for (i = 1; i < n; i++ )
        for (j = 0; j < i; j++ )
            if ( (arr[i] == (arr[j]-1)) && lis[i] < lis[j] + 1)
                lis[i] = lis[j] + 1;

    /* Pick maximum of all LIS values */
    for (i = 0; i < n; i++ )
        if (max < lis[i])
            max = lis[i];

    /* Free memory to avoid memory leak */
    free(lis);

    return max;
}
int main()
{
in
vin
sorta
vi arr1;
    int count =1;
for(int i=0;i<n;i++)
{ count =1;
    for(int j=i+1;j<n;j++)
    {

        if((arr[j]-arr[i])<=1)
        count++;
        else
        {
            break;
        }

    }
    arr1.pb(count);

}
cout<<*max_element(arr1.begin(),arr1.end());




}