#include <bits/stdc++.h>
using namespace std;
typedef long long int LL;
typedef unsigned long long int uLL;
inline int _Int() { int x; scanf("%d",&x); return x; }
LL bigMod(LL A,LL P,int M){ LL R=1; for(A%=M; P; P>>=1) { if(P&1) R=(R*A)%M; A=(A*A)%M; } return R; } /** (A^P) % M **/
LL bigMul(LL A,LL B,LL M) { LL R=0; for(A%=M; B; B>>=1) { if(B&1) R=(R+A)%M; A=(A+A)%M; } return R; } /** (A*B) % M **/
LL negMod(LL A,LL B) { return ( ( ( A % B ) + B) % B ); } /** (A % B) when A is negative or positive **/
LL invMod(LL A,LL M) { return bigMod( A , M-2, M ); } /** (A^(-1)) % M */
uLL _pow(uLL A,int P) { uLL R=1; for(; P; P>>=1) { if(P&1) R=(R*A); A=(A*A); } return R; } /** (A^P) **/
template<class T>T GCD(T x, T y) { while(x) x^=y^=x^=y%=x; return y; } /** Greatest Common Divisor( a , b ) **/
template<class T> bool inRng( T u, T v, T x ) { return u<=x && x<=v; } /** check ( u <= x <=v ) */
#define myMemset(a,b) memset(a,b,sizeof(a))
#define pi            acos(-1)
#define pb            push_back
#define myDebug(x)    cout<<#x<<" : "<<x<<"\n"
/*************************************************************************************************************************
**                                            Syed Zafrul Lipu (ShockProof)                                              *
**                                            CSE, University of Asia Pacific                                            *
**************************************************************************************************************************/

int n;
int fr[1000];

void Main()
{
    n = _Int();
    for(int i=0; i<n; i++) {
        fr[ _Int() ] ++;
    }
    
    int Ans = 0;
    
    for(int i=1; i<=100; i++) {
        Ans = max( Ans , fr[i]+fr[i-1] );
    }
    printf("%d\n",Ans);
}

int main()
{
    Main();
    return 0;
}