import java.util.Scanner;
public class A {

	public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();

        int[] ar = new int[n];
        for(int i=0;i<n;i++){
        	ar[i] = in.nextInt();

        }
        int[] ar1 = sort(ar);
        int found = 0;
        int max = 1;
        int a0 = ar1[0];
        int cont = 1;
        for(int i=1;i<ar1.length;i++){
        	int a1 = ar1[i];
        	if((a1-a0)<= 1) {
        		if(found ==0) {
        			found++;
        		} else {
        			
        		}
        		cont++;
        		if(max < cont) max = cont;
        	}
        	else {
        		cont = 1;
            	a0 = a1;
        	}
        }
        System.out.println(max);
	}


	static int[] sort(int[] ar){
		int len = ar.length;
		int mid = len/2;
		
		if(ar.length == 1){
			return ar;
		}else{
			int[] a = new int[mid];
			int[] b = new int[len-mid];
			int a_cnt = 0;
			int b_cnt = 0;
			for(int i=0;i<len;i++){
				if(i<mid){
					a[a_cnt++] = ar[i];
				}
				else{
					b[b_cnt++] = ar[i];
				}
			}
			int[] l = sort(a);
			int[] r = sort(b);
			int[] m = merge(l,r);
			return m;
		}
		
	}
	
	static int[] merge(int[]a, int[]b){
		int[] s = new int[a.length + b.length];
		int i=0,j=0,idx = 0;

		while(i<a.length && j<b.length){
			if(a[i] <= b[j]) s[idx++] = a[i++];
			else s[idx++] = b[j++];
		}
		
		if(i<a.length && j==b.length)
			while(i<a.length) s[idx++] = a[i++];
		
		if(j<b.length && i==a.length) 
			while(j<b.length) s[idx++] = b[j++];
		
		return s;
	}
	
}