#!/usr/bin/env python3

n, lph = [int(x) for x in input().strip().split()]
problems = []
for _ in range(n):
    problems.append( int( input().strip() ) )
problems.sort()

max_probs = 0
total_time = 0
target = 5*lph
for problem in problems:
    total_time += problem
    if total_time<=target:
        max_probs += 1
    else:
        break

print( max_probs )