#include <cstdio>

int main() {
	int n;
	int p[100];
	scanf("%d", &n);
	for (int i = 0; i < n; i++) {
		int a;
		scanf("%d", &a);
		p[i] = a;
	}
	
	int resp = 0;
	
	for (int a = 0; a < 100; a++) {
		int aux = 0;
		for (int i = 0; i < n; i++) {
			if (p[i] == a || p[i] == a+1)
				aux++;
		}
		if (aux > resp)
			resp = aux;
	}
	
	printf("%d\n", resp);
	
	/*
	for (int i = 0; i < (1 << n); i++) {
		for (int j = 0; j < n; j++) {
			if (i & (1 << j)) {
				printf("%d", p[j]);
			}
		}
		printf("\n");
	}
	*/
}