#51292: 7s yeah!
pikachuchen318@gmail.com
(sseb)
學校
:
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編號 : 314919
來源 : [218.173.15.217]
最後登入時間 ：
2025-08-13 15:03:16
def prime(n):
if n == 1:
return 0
else:
if n % 2 == 0 and n != 2:
return 0
else:
if n % 3 == 0 and n != 3:
return 0
else:
for i in range(5, int(n**0.5)+1, 6):
if n % i == 0: #5 11 17
return 0
if n % (i+2) == 0: #7 13 19
return 0
return 1
while True:
try:
a, b = map(int, input().split())
if b - a > 1000:
print(0)
break
count = 0
for i in range(a, b+1):
count += prime(i)
print(count)
except(EOFError):
break