python 代码

a,b = map(int,input().split())
for num in range(b,a,-1):
    success = True
    j = 2
    while j <= a and j**2 <= num:
        if num  % j == 0:
            success = False
            break
        j = j + 1
    if success == True:
        print(num)
        exit()

print(-1)

# ------------------------- 线性筛法，但爆空间------------------------------------------#
# a,b = map(int,input().split())
# def get_primes(n):
#     primes = []
#     cnt = 0
#     st = [False] * (n + 1)
#     for i in range(2,n + 1):
#         if st[i] == False:
#             primes.append(i)
#             cnt = cnt + 1
#         j = 0
#         while j < cnt and primes[j] * i <= n:
#             t = primes[j] * i
#             st[t] = True
#             if i % primes[j] == 0:
#                 break
#             j = j + 1
#     return primes
# primes_b = get_primes(b)
# primes_a = get_primes(a)
# ans = primes_b[-1]
# for num in range(b,ans - 1,-1):
#     u = False
#     if ans <= a:
#         print(-1)
#         break
#     for d in primes_a:
#         if num % d == 0:
#             u = True
#             break
#     if u == True:
#         continue
#     else:
#         print(num)
#         exit()