#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>
#define si(a) scanf("%d",&a)
#define sf(a) scanf("%f",&a)
#define sc(a) scanf("%d",&c)


#define si2(x,y) scanf("%d%d",&x,&y)
#define si3(x,y,z) scanf("%d%d%d",&x,&y,&z)

#define sll1(x) scanf("%lld",&x)
#define sll2(x,y) scanf("%lld%lld",&x,&y)
#define sll3(x,y,z) scanf("%lld%lld%lld",&x,&y,&z)

#define pri(x) printf("%d\n",x)
#define pri2(x,y) printf("%d %d\n",x,y)
#define pri3(x,y,z) printf("%d %d %d\n",x,y,z)

#define prll1(x) printf("%lld\n",x)
#define prll2(x,y) printf("%lld %lld\n",x,y)
#define prll3(x,y,z) printf("%lld %lld %lld\n",x,y,z)

#define fi(i,j) for(i=0;i<j;i++)
#define fd(i,j) for(i=j;i>0;i--)
#define fi1(i,j,k) for(i=j;i<k;i++)
#define fd1(i,j,k) for(i=j;i>k;i--)
typedef long long int ll;
int main(){
    int n,b[100],i,sum,smax=0;
    fi(i,100){
        b[i]=0;
    }
    scanf("%d",&n);
    int *a = malloc(sizeof(int) * n);
    for(int a_i = 0; a_i < n; a_i++){
       scanf("%d",&a[a_i]);
        b[a[a_i]]++;
    }
    fi(i,99){
        sum = b[i]+ b[i+1];
        if(sum>smax)
            smax = sum;
        
    }
    pri(smax);
    return 0;
}