https://www.acmicpc.net/problem/1978 # -*- encoding: cp949 -*- def prime_number(max_n): p = [0 for i in xrange(max_n+1)] for i in xrange(2,max_n+1): for j in xrange(i,max_n+1,i): if j!=i: p[j] = 1 prime = [i for i in xrange(2,max_n+1) if p[i]==0] return prime input() n = map(int,raw_input().split()) print len([i for i in n if i in set(prime_number(1000))]) https://www.acmicpc.net/problem/2960 # ..