2813 : 소수의 개수
def eratos(b): global prime prime[0]=1 prime[1]=1 for i in range(2,b+1): if(prime[i]>0) : continue for j in range(i*i,b+1,i): prime[j]=1 prime = [0 for i in range(2000000 +1)] eratos(2000000) n,m = map(int,input().split()) cnt=0 for i in range(n,m+1): if prime[i]==0:cnt+=1 print(cnt)